gistfile1.php

add_filter( 'woocommerce_cart_shipping_packages', 'bulky_woocommerce_cart_shipping_packages' );

function bulky_woocommerce_cart_shipping_packages( $packages ) {
    // Reset the packages
    $packages = array();
  
    // Bulky items
    $bulky_items = array();
    $regular_items = array();
    
    // Sort bulky from regular
    foreach ( WC()->cart->get_cart() as $item ) {
        if ( $item['data']->needs_shipping() ) {
            if ( $item['data']->get_shipping_class() == 'bulky' ) {
                $bulky_items[] = $item;
            } else {
                $regular_items[] = $item;
            }
        }
    }
    
    // Put inside packages
    if ( $bulky_items ) {
        $packages[] = array(
            'ship_via' => array( 'flat_rate' ),
            'contents' => $bulky_items,
            'contents_cost' => array_sum( wp_list_pluck( $bulky_items, 'line_total' ) ),
            'applied_coupons' => WC()->cart->applied_coupons,
            'destination' => array(
                'country' => WC()->customer->get_shipping_country(),
                'state' => WC()->customer->get_shipping_state(),
                'postcode' => WC()->customer->get_shipping_postcode(),
                'city' => WC()->customer->get_shipping_city(),
                'address' => WC()->customer->get_shipping_address(),
                'address_2' => WC()->customer->get_shipping_address_2()
            )
        );
    }
    if ( $regular_items ) {
        $packages[] = array(
            'contents' => $regular_items,
            'contents_cost' => array_sum( wp_list_pluck( $regular_items, 'line_total' ) ),
            'applied_coupons' => WC()->cart->applied_coupons,
            'destination' => array(
                'country' => WC()->customer->get_shipping_country(),
                'state' => WC()->customer->get_shipping_state(),
                'postcode' => WC()->customer->get_shipping_postcode(),
                'city' => WC()->customer->get_shipping_city(),
                'address' => WC()->customer->get_shipping_address(),
                'address_2' => WC()->customer->get_shipping_address_2()
            )
        );
    }    
    
    return $packages;
}