How can I create a custom Gutenberg block in WordPress?

<!-- BEGIN COPY / PASTE -->
    // Enqueue block scripts
    function my_custom_block() {
      wp_register_script(
        'my-block-script',
        get_template_directory_uri() . '/js/my-block.js',
        array('wp-blocks', 'wp-element', 'wp-editor'),
        filemtime(get_template_directory() . '/js/my-block.js')
      );

      register_block_type('myplugin/my-custom-block', array(
        'editor_script' => 'my-block-script',
      ));
    }
    add_action('init', 'my_custom_block');
    <!-- END COPY / PASTE -->