Remove /product/ base

/**
 * Detect product permalinks
 */
function pm_detect_post_slugs($query) {
    global $wpdb, $pm_query;

    if(!empty($pm_query['uri'])) {
        $post_name = basename($pm_query['uri']);

        $sql_query = $wpdb->prepare(
            "SELECT post_name FROM $wpdb->posts WHERE post_name = %s AND post_type = 'product'",
            array($post_name)
        );
        $uri = $wpdb->get_var($sql_query);

        if(!empty($uri)) {
            $page = (!empty($query['page'])) ? $query['page'] : 1;
            $new_query = array(
                'product' => $uri,
                'post_type' => 'product',
                'name' => $uri,
                'page' => $page,
                'do_not_redirect' => 1,
            );

            // Disable canonical redirect
            remove_action('template_redirect', 'wp_old_slug_redirect');
            remove_action('template_redirect', 'redirect_canonical');
            add_filter('wpml_is_redirected', '__return_false', 99, 2);
            add_filter('pll_check_canonical_url', '__return_false', 99, 2);

            return $new_query;
        }
    }

    return $query;
}
add_filter('request', 'pm_detect_post_slugs');

/**
* Filter product permalinks
*/
function bis_filter_product_permalinks($url, $element) {
    if(!empty($element->post_type) && ($element->post_type == 'product')) {
        $home_base = trim(get_option('home'), '/');

        // $url = preg_replace('/(http(?:s)?:\/\/(?:www\.)?[^\/]+\/)([^\/]+)\/([^\/]+)/', '$1$3', $url);
        $url = "{$home_base}/{$element->post_name}";
    }

    return user_trailingslashit($url);
}
add_filter('post_type_link', 'bis_filter_product_permalinks', 999, 2);