Simple ACF Gutenberg Block

acf-test-block.php

<?php
/* Plugin Name: ACF 5.8 Test
*/

class ACF_Test_Block {

	public $_name = 'test-acf-block';

	public function __construct() {
		add_action( 'acf/init', [ $this, 'register_block' ] );
		add_action( 'acf/init', [ $this, 'register_fields' ] );
	}

	public function register_block() {

		// register a testimonial block.
		acf_register_block_type(
			array(
				'name'            => $this->_name,
				'title'           => __( 'Test ACF Block' ),
				'description'     => __( 'Test ACF Block' ),
				'render_callback' => [ $this, 'render_block' ],
				'category'        => 'formatting',
				'icon'            => 'admin-comments',
				'keywords'        => array( 'acf', 'test' ),
				'enqueue_style' => plugin_dir_url(__FILE__) . '/test-field.css',
			)
		);

	}


	public function register_fields() {
		acf_add_local_field_group(
			array(
				'key'      => 'test_settings',
				'title'    => 'Test Settings',
				'fields'   => array(
					array(
						'key'   => 'test_field',
						'label' => 'Enter some text here',
						'name'  => 'test_field_text',
						'type'  => 'text',
					),
					array(
						'key'           => 'test_image',
						'label'         => 'Add an image',
						'name'          => 'test_field_image',
						'type'          => 'image',
						'return_format' => 'id',
					),
				),
				'location' => array(
					array(
						array(
							'param'    => 'block',
							'operator' => '==',
							'value'    => 'acf/' . $this->_name,
						),
					),
				),
			)
		);
	}

	public function render_block() {
		$image_id = get_field( 'test_field_image' );

		echo '<div class="'.$this->_name.'">';
			if (false !== $image_id) {
				echo wp_get_attachment_image($image_id);
			}
			echo '<h5>'.get_field( 'test_field_text' ) . '</h5>';
		echo '</div>';



	}
}

new ACF_Test_Block();

test-field.css

.test-acf-block {
    display: flex;
}
.test-acf-block img {
    margin-right: 10px;
}