This file (included in functions.php) adds a Post Listing block using ACF. Key points of customization:

post-listing.php

<?php
/**
 * Post Listing
 *
 * @package      CultivateBlocks
 * @author       Bill Erickson
 * @since        1.0.0
 * @license      GPL-2.0+
**/

class BE_Post_Listing {

	/**
	 * Refers to a single instance of this class
	 *
	 * @var null
	 */
	private static $instance = null;

	/**
	 * Layouts
	 *
	 * @var array
	 */
	private $layouts = [];

	/**
	 * Taxonomies
	 *
	 * @var array
	 */
	private $taxonomies = [];

	/**
	 * Creates or returns an instance of this class.
	 *
	 * @since 0.1.8
	 * @return object BE_Post_Listing, a single instance of this class.
	 */
	public static function instance() {
		if ( null == self::$instance ) {
			self::$instance = new self;
		}
		return self::$instance;
	}

	/**
	 * Construct
	 *
	 * @since 0.1.0
	 */
	function __construct() {

		$this->setup();

		// Create block
		add_action('acf/init', array( $this, 'register_block' ) );

	}

	/**
	 * Setup Layouts and Taxonomies
	 *
	 */
	function setup() {
		$this->layouts = [
			'alpha'		=> [
				'label'				=> '3 Column',
				'posts_per_page'	=> 3,
				'partial'			=> 'primary',
			],
			'beta'		=> [
				'label'				=> '4 Column',
				'posts_per_page'	=> 4,
				'partial'			=> 'tertiary',
			],
			'gamma'		=> [
				'label'				=> '2x2 Grid',
				'posts_per_page'	=> 4,
				'partial'			=> 'secondary',
			],
			'delta'		=> [
				'label'				=> 'Feature',
				'posts_per_page'	=> 4,
				'partial'			=> 'secondary',
				'partial_override'	=> [
					0 => 'feature',
				]
			],
		];

		$this->taxonomies = [
			[
				'tax'		=> 'category',
				'field'		=> 'category',
				'label'		=> 'Category',
			],
			[
				'tax'		=> 'post_tag',
				'field'		=> 'post_tag',
				'label'		=> 'Tag',
			]
		];
	}

	/**
	 * Register post listing block
	 *
	 */
	function register_block() {

		acf_register_block_type( array(
			'name'				=> 'post-listing',
			'title'				=> __( 'Post Listing', 'cultivate_textdomains' ),
			'render_callback'	=> array( $this, 'post_listing_block' ),
			'category'			=> 'cultivatewp',
			'icon'				=> be_icon( [ 'icon' => 'cultivatewp', 'group' => 'color', 'size' => 24 ] ),
			'mode'				=> 'auto',
			'supports'			=> [ 'anchor' => false, 'align' => false ]
		));

		$layout_choices = [];
		foreach( $this->layouts as $layout => $atts ) {
			$layout_choices[ $layout ] = $atts['label'];
		}

		$fields = array(
			array(
				'key' => 'field_5e6a893b53d10',
				'label' => 'Title',
				'name' => 'title',
				'type' => 'text',
				'instructions' => '',
				'required' => 0,
				'conditional_logic' => 0,
				'wrapper' => array(
					'width' => '',
					'class' => '',
					'id' => '',
				),
				'default_value' => '',
				'placeholder' => '',
				'prepend' => '',
				'append' => '',
				'maxlength' => '',
			),
			array(
				'key' => 'field_5e6a894753d11',
				'label' => 'Layout',
				'name' => 'layout',
				'type' => 'select',
				'instructions' => '',
				'required' => 0,
				'conditional_logic' => 0,
				'wrapper' => array(
					'width' => '',
					'class' => '',
					'id' => '',
				),
				'choices' => $layout_choices,
				'default_value' => array(
				),
				'allow_null' => 0,
				'multiple' => 0,
				'ui' => 0,
				'return_format' => 'value',
				'ajax' => 0,
				'placeholder' => '',
			),
			array(
				'key' => 'field_5e6a895053d12',
				'label' => 'Order',
				'name' => 'orderby',
				'type' => 'select',
				'instructions' => '',
				'required' => 0,
				'conditional_logic' => 0,
				'wrapper' => array(
					'width' => '',
					'class' => '',
					'id' => '',
				),
				'choices' => array(
					'recent' => 'Recent',
					'popular' => 'Popular',
					'manual' => 'Manual',
				),
				'default_value' => array(
				),
				'allow_null' => 0,
				'multiple' => 0,
				'ui' => 0,
				'return_format' => 'value',
				'ajax' => 0,
				'placeholder' => '',
			),
			array(
				'key' => 'field_5e6a897453d13',
				'label' => 'Posts',
				'name' => 'post__in',
				'type' => 'post_object',
				'instructions' => '',
				'required' => 0,
				'conditional_logic' => array(
					array(
						array(
							'field' => 'field_5e6a895053d12',
							'operator' => '==',
							'value' => 'manual',
						),
					),
				),
				'wrapper' => array(
					'width' => '',
					'class' => '',
					'id' => '',
				),
				'post_type' => array(
					0 => 'post',
				),
				'taxonomy' => '',
				'allow_null' => 1,
				'multiple' => 1,
				'return_format' => 'id',
				'ui' => 1,
			),
			array(
				'key' => 'field_8e6a893b53d10',
				'label' => 'Read More',
				'name' => 'read_more',
				'type' => 'text',
				'instructions' => '',
				'required' => 0,
				'conditional_logic' => 0,
				'wrapper' => array(
					'width' => '',
					'class' => '',
					'id' => '',
				),
				'default_value' => '',
				'placeholder' => '',
				'prepend' => '',
				'append' => '',
				'maxlength' => '',
			),

		);

		foreach( $this->taxonomies as $i => $taxonomy ) {
			$fields[] = [
				'key' => 'field_5e6a8aa253d2' . $i,
				'label' => 'Limit to ' . $taxonomy['label'],
				'name' => $taxonomy['field'],
				'type' => 'taxonomy',
				'instructions' => '',
				'required' => 0,
				'conditional_logic' => 0,
				'taxonomy' => $taxonomy['tax'],
				'field_type' => 'multi_select',
				'all_null' => 1,
				'add_term' => 0,
				'save_terms' => 0,
				'load_terms' => 0,
				'return_format' => 'id',
				'multiple' => 1,
			];
		}

		acf_add_local_field_group(array(
			'key' => 'group_5e6a89326b7cb',
			'title' => 'Post Listing Block',
			'fields' => $fields,
			'location' => array(
				array(
					array(
						'param' => 'block',
						'operator' => '==',
						'value' => 'acf/post-listing',
					),
				),
			),
			'menu_order' => 0,
			'position' => 'normal',
			'style' => 'default',
			'label_placement' => 'top',
			'instruction_placement' => 'label',
			'hide_on_screen' => '',
			'active' => true,
			'description' => '',
		));

	}

	/**
	 * Post Listing Block
	 *
	 */
	function post_listing_block( $block, $content = '', $is_preview = false, $post_id = 0 ) {

		$settings = [
			'title'		=> get_field( 'title' ),
			'layout'	=> get_field( 'layout' ),
			'orderby'	=> get_field( 'orderby' ),
			'post__in'	=> get_field( 'post__in' ),
			'title'		=> get_field( 'title' ),
			'read_more'	=> get_field( 'read_more' )
		];

		foreach( $this->taxonomies as $taxonomy ) {
			$settings[ $taxonomy['field'] ] = get_field( $taxonomy['field'] );
		}

		if( !empty( $block['className'] ) )
			$settings['className'] = $block['className'];
		if( !empty( $block['anchor'] ) )
			$settings['anchor']	= $block['anchor'];


		$this->display( $settings );

	}

	/**
	 * Display
	 *
	 */
	function display( $settings = [] ) {

		$classes = ['block-post-listing'];
		if( !empty( $settings['className'] ) )
		    $classes = array_merge( $classes, explode( ' ', $settings['className'] ) );
		if( !empty( $settings['layout'] ) )
			$classes[] = 'layout-' . $settings['layout'];

		$anchor = '';
		if( !empty( $settings['anchor'] ) )
			$anchor = ' id="' . sanitize_title( $settings['anchor'] ) . '"';

		$loop = new WP_Query( $this->query_args( $settings ) );
		if( ! $loop->have_posts() )
			return;

		echo '<section class="' . join( ' ', $classes ) . '"' . $anchor . '>';

			if( !empty( $settings['title'] ) )
				echo '<header><h2>' . esc_html( $settings['title'] ) . '</h2></header>';

			echo '<div class="block-post-listing__inner">';
			while( $loop->have_posts() ): $loop->the_post();
				$partial = $this->partial( $settings['layout'], $loop->current_post );
				get_template_part( 'partials/post-summary/' . $partial );
			endwhile;
			wp_reset_postdata();
			echo '</div>';

			$this->display_footer( $settings );
		echo '</section>';

	}

	/**
	 * Display Footer
	 *
	 */
	function display_footer( $settings = [] ) {
		if( empty( $settings['read_more'] ) )
			return;

		$has_tax = $link = false;
		foreach( $this->taxonomies as $taxonomy ) {
			if( !empty( $settings[ $taxonomy['field'] ] ) ) {
				$has_tax = true;
				$terms = $settings[ $taxonomy['field'] ];
				if( ! is_array( $terms ) )
					$terms = array( $terms );
				if( 1 < count( $terms ) )
					return false;
				$term = get_term_by( 'id', $terms[0], $taxonomy['tax'] );
				if( empty( $term ) || is_wp_error( $term ) || !empty( $more_link ) )
					return false;

				$link = get_term_link( $term, $taxonomy['tax'] );
			}
		}

		if( ! $has_tax && get_option( 'page_for_posts' ) && ( empty( $settings['post_type' ] ) || 'post' === $settings['post_type'] ) )
			$link = get_permalink( get_option( 'page_for_posts' ) );

		if( ! $has_tax && !empty( $settings['post_type'] ) && 'post' !== $settings['post_type'] )
			$link = get_post_type_archive_link( $settings['post_type'] );

		if( !empty( $link ) )
			echo '<footer><a href="' . esc_url( $link ) . '">' . esc_html( $settings['read_more'] ) . '</a></footer>';

	}

	/**
	 * Query Arguments
	 *
	 */
	function query_args( $settings ) {

		$args = [
			'posts_per_page'	=> 4,
			'post_status'		=> 'publish',
		];

		if( !empty( $settings['post__not_in'] ) )
			$args['post__not_in'] = $settings['post__not_in'];

		if( !empty( $settings['layout'] ) && array_key_exists( $settings['layout'], $this->layouts ) )
			$args['posts_per_page'] = $this->layouts[ $settings['layout'] ]['posts_per_page'];

		if( !empty( $settings['orderby'] ) && 'popular' === $settings['orderby'] ) {

			// Order by comment count
			$args['orderby'] = 'comment_count';

			/*
			// Order by share count
			$args['orderby'] = 'meta_value_num';
			$args['meta_key'] = 'shared_counts_total';
			*/

			/*
			// Limit by post date
			$args['date_query'] = array(
				array(
					'after' => '-3 months',
				)
			);
			*/
		}

		foreach( $this->taxonomies as $taxonomy ) {
			if( !empty( $settings[ $taxonomy['field'] ] ) ) {
				$terms = $settings[ $taxonomy['field'] ];
				if( ! is_array( $terms ) )
					$terms = array( $terms );

				$tax_args = [
					'taxonomy'	=> $taxonomy['tax'],
					'field'		=> 'term_id',
					'terms'		=> $terms,
					'include_children' => true,
				];
				if( 1 < count( $tax_args['terms'] ) ) {
					$tax_args['operator'] = 'AND';
					$tax_args['include_children'] = false;
				}
				$args['tax_query'][] = $tax_args;
			}
		}

		if( !empty( $settings['orderby'] ) && 'manual' === $settings['orderby'] ) {
			if( !empty( $args['tax_query'] ) )
				unset( $args['tax_query'] );

			if( empty( $settings['post__in'] ) )
				$post_ids = [ 1 ]; // no post with ID = 1, will return no results
			elseif( ! is_array( $settings['post__in'] ) )
				$post_ids = [ intval( $settings['post__in'] ) ];
			else
				$post_ids = array_map( 'intval', $settings['post__in'] );

			$args['post__in'] = $post_ids;
			$args['orderby'] = 'post__in';

		}

		return $args;
	}

	/**
	 * Partial
	 *
	 */
	function partial( $layout = false, $current_post = 0 ) {
		$partial = false;

		if( ! $layout )
			return $partial;

		if( empty( $this->layouts[ $layout ] ) )
			return $partial;

		$layout = $this->layouts[ $layout ];

		// Post specific partial
		if( !empty( $layout['partial_override'] ) && !empty( $layout['partial_override'][ $current_post ] ) )
			$partial = $layout['partial_override'][ $current_post ];

		// Layout specific partial
		if( empty( $partial ) )
			$partial = $layout['partial'];

		return $partial;

	}
}

function be_post_listing() {
	return BE_Post_Listing::instance();
}
be_post_listing();