Register and display a new widget area in Genesis. Source: https://my.studiopress.com/documentation/tutorials/widget-areas/register-a-widget-area/

register-widget-area-genesis.php

<?php

//* Register After Post widget area
genesis_register_sidebar( array(
	'id'            => 'after-post',
	'name'          => __( 'After Post', 'themename' ),
	'description'   => __( 'This is a widget area that can be placed after the post', 'themename' ),
) );

//* Hook After Post widget area after post content
add_action( 'genesis_entry_footer', 'customprefix_after_post_widget' );
function customprefix_after_post_widget() {
	if ( is_singular( 'post' ) ) {
		genesis_widget_area( 'after-post', array(
			'before' => '<div class="after-post widget-area">',
			'after' => '</div>',
		) );
	}
}