Wordpress - Display featured products through custom loop in woocommerce on template page

This has changed in WooCommerce 3.0. It's not simply a meta_query, but now includes a tax_query. The arguments are now:

    $meta_query  = WC()->query->get_meta_query();
    $tax_query   = WC()->query->get_tax_query();
    $tax_query[] = array(
        'taxonomy' => 'product_visibility',
        'field'    => 'name',
        'terms'    => 'featured',
        'operator' => 'IN',
    );

    $args = array(
        'post_type'           => 'product',
        'post_status'         => 'publish',
        'ignore_sticky_posts' => 1,
        'posts_per_page'      => $atts['per_page'],
        'orderby'             => $atts['orderby'],
        'order'               => $atts['order'],
        'meta_query'          => $meta_query,
        'tax_query'           => $tax_query,
    );

See woocommerce/includes/class-wc-shortcodes.php

Change your args to be like this:

$meta_query   = WC()->query->get_meta_query();
$meta_query[] = array(
    'key'   => '_featured',
    'value' => 'yes'
);
$args = array(
    'post_type'   =>  'product',
    'stock'       =>  1,
    'showposts'   =>  6,
    'orderby'     =>  'date',
    'order'       =>  'DESC',
    'meta_query'  =>  $meta_query
);

If you go to wp-content/plugins/woocommerce/includes/class-wc-shortcodes.php (@595) you can find how it's done for WC shortcodes.

Featured Products Loop in WooCommerce 3

<ul class="products">
<?php
$args = array(
    'post_type' => 'product',
    'posts_per_page' => 12,
    'tax_query' => array(
            array(
                'taxonomy' => 'product_visibility',
                'field'    => 'name',
                'terms'    => 'featured',
            ),
        ),
    );
$loop = new WP_Query( $args );
if ( $loop->have_posts() ) {
    while ( $loop->have_posts() ) : $loop->the_post();
        wc_get_template_part( 'content', 'product' );
    endwhile;
} else {
    echo __( 'No products found' );
}
wp_reset_postdata();
?>