A basic server rendered block, like a shortcode but blocks!

block.js

( function( wp ) {
	var el = wp.element.createElement;
	wp.blocks.registerBlockType( 'tomjn/dynamic', {
		title: 'Toms Dynamic Block',
		edit: function( props ) {
			return el( wp.serverSideRender, {
				block: 'tomjn/dynamic',
				attributes: props.attributes,
			} );
		},
	} );
}( window.wp ));

plugin.php

<?php
/**
* Plugin Name: Server Rendered Block Example
* Description: Like a shortcode but it's a block!
*/

function render_toms_block( array $attributes, $content ) : string {
	return "Hello World!";
}

function register_toms_block() {
	// Register the JS.
	wp_register_script(
		'toms-block-js',
		plugins_url( 'block.js', __FILE__ ),
		[ 'wp-blocks', 'wp-element' ]
	);

	// Register the block.
	register_block_type(
		'tomjn/dynamic',
		[
			'editor_script'   => 'toms-block-js',
			'render_callback' => 'render_toms_block',
		]
	);
}
add_action( 'init', 'register_toms_block' );