Sample simple shop setup with a flexible grid

archive-product.php

<?php

/**
 * Archive page for products (custom post type).
 *
 */

remove_action( 'genesis_entry_header', 'genesis_post_info', 12 );
remove_action( 'genesis_entry_content', 'genesis_do_post_image', 8 );
remove_action( 'genesis_entry_footer', 'genesis_post_meta' );

add_filter( 'genesis_pre_get_option_content_archive', 'rgc_do_full_content' );
function rgc_do_full_content() {
	return 'full';
}

add_filter( 'genesis_pre_get_option_content_archive_limit', 'rgc_no_content_limit' );
function rgc_no_content_limit() {
	return '0';
}

add_filter( 'post_class', 'rgc_grid_post_class' );
function rgc_grid_post_class( $classes ) {
	global $wp_query;

	if ( ! $wp_query->is_main_query() ) {
		return $classes;
	}

	$term         = $wp_query->get_queried_object();
	$layout       = genesis_site_layout( $term );
	$number       = 2;
	$column_class = 'one-half';

	if ( in_array( $layout, array( __genesis_return_sidebar_content(), __genesis_return_content_sidebar() ) ) ) {
		$number       = 3;
		$column_class = 'one-third';
	}

	elseif ( __genesis_return_full_width_content() === $layout ) {
		$number       = 4;
		$column_class = 'one-fourth';
	}


	$classes[] = 'grid ' . $column_class;

	if ( 0 == $wp_query->current_post % $number ) {
		$classes[] = 'first';
	}

	return $classes;
}

add_action( 'genesis_entry_header', 'rgc_posts_grid', 5 );
function rgc_posts_grid() {
	global $post;

	if ( $image = genesis_get_image( 'format=url&size=product' ) ) {
		printf( '<div class="grid-image"><a href="%s" target="_blank" rel="bookmark"><img src="%s" alt="%s" class="aligncenter" /></a></div>', get_permalink(), $image, the_title_attribute( 'echo=0' ) );
	}
	else {
		printf( '<div class="grid-image"><a href="%s" target="_blank" rel="bookmark"><img src="%s" alt="%s" class="aligncenter" /></a></div>', get_permalink(), get_bloginfo( 'stylesheet_directory' ) . '/images/blank.jpg', the_title_attribute( 'echo=0' ) );
	}

}

genesis();

style.css

/* Grid
--------------------------------------------- */

.entry.grid {
	margin-bottom: 24px;
	padding: 24px;
	border: 1px solid #ddd;
	border-radius: 0;
	font-size: 16px;
	text-align: center;
}

.grid .entry-title {
	font-size: 24px;
}