Use this as a basis for a single blocksy template part in child theme

blocsky-single.php

<?php
/*
 * The template for displaying all single posts
 *
 * @link https://developer.wordpress.org/themes/basics/template-hierarchy/#single-post
 *
 * @package Blocksy
 */

if (have_posts()) {
	the_post();
}

/**
 * Note to code reviewers: This line doesn't need to be escaped.
 * Function blocksy_output_hero_section() used here escapes the value properly.
 */
if (apply_filters('blocksy:single:has-default-hero', true)) {
	echo blocksy_output_hero_section([
		'type' => 'type-2'
	]);
}

$page_structure = blocksy_get_page_structure();

$container_class = 'ct-container-full';
$data_container_output = '';

if ($page_structure === 'none' || blocksy_post_uses_vc()) {
	$container_class = 'ct-container';

	if ($page_structure === 'narrow') {
		$container_class = 'ct-container-narrow';
	}
} else {
	$data_container_output = 'data-content="' . $page_structure . '"';
}

ob_start();
the_content(
	sprintf(
		wp_kses(
			/* translators: %s: Name of current post. Only visible to screen readers */
			__( 'Continue reading<span class="screen-reader-text"> "%s"</span>', 'blocksy' ),
			array(
				'span' => array(
					'class' => array(),
				),
			)
		),
		get_the_title()
	)
);
$post_content = ob_get_clean();

?>
<div
		class="<?php echo trim($container_class) ?>"
		<?php echo wp_kses_post(blocksy_sidebar_position_attr()); ?>
		<?php echo $data_container_output; ?>
		<?php echo blocksy_get_v_spacing() ?>>
		<?php do_action('blocksy:single:container:top'); ?>
		<?php
		/**
     * Note to code reviewers: This line doesn't need to be escaped.
     * Function blocksy_single_content() used here escapes the value properly.
     * It adds te header, categories and other elements as well as the share and related content
     * Not ideal.
     */
			$post_content = do_shortcode('[custom_shortcode]');

			echo blocksy_single_content($post_content);
		?>

		<?php get_sidebar(); ?>

		<?php do_action('blocksy:single:container:bottom'); ?>
  	</div>

<?php

blocksy_display_page_elements('separated');

have_posts();
wp_reset_query();