Add custom field data to WooCommerce

I am currently successfully adding a field to my WooCommerce product which is showing in the cart, checkout, order page and admin order. For some reason it isn't showing as a custom field in the admin order, just as text.

Here is my working code:

// Add the field to the product
add_action('woocommerce_before_add_to_cart_button', 'my_custom_checkout_field');

function my_custom_checkout_field() {
    echo '<div id="my_custom_checkout_field"><h3>'.__('My Field').'</h3>';
    echo  '<label>fill in this field</label> <input type="text" name="my_field_name">';
    echo '</div>';
}

// Store custom field
function save_my_custom_checkout_field( $cart_item_data, $product_id ) {
    if( isset( $_REQUEST['my_field_name'] ) ) {
        $cart_item_data[ 'my_field_name' ] = $_REQUEST['my_field_name'];
        /* below statement make sure every add to cart action as unique line item */
        $cart_item_data['unique_key'] = md5( microtime().rand() );
    }
    return $cart_item_data;
}
add_action( 'woocommerce_add_cart_item_data', 'save_my_custom_checkout_field', 10, 2 );

// Render meta on cart and checkout
function render_meta_on_cart_and_checkout( $cart_data, $cart_item = null ) {
    $custom_items = array();
    /* Woo 2.4.2 updates */
    if( !empty( $cart_data ) ) {
        $custom_items = $cart_data;
    }
    if( isset( $cart_item['my_field_name'] ) ) {
        $custom_items[] = array( "name" => 'My Field', "value" => $cart_item['my_field_name'] );
    }
    return $custom_items;
}
add_filter( 'woocommerce_get_item_data', 'render_meta_on_cart_and_checkout', 10, 2 );

// This is what I think needs changing?

function subscription_order_meta_handler( $item_id, $values, $cart_item_key ) {
    if( isset( $values['my_field_name'] ) ) {
        wc_add_order_item_meta( $item_id, "My Field", $values['my_field_name'] );
    }
}
add_action( 'woocommerce_add_order_item_meta', 'subscription_order_meta_handler', 1, 3 );

I think it is this last bit of the code that needs changing. It currently shows the text under the order item, so perhaps I need to adjust

wc_add_order_item_meta

to something else? I've tried everything but it doesn't seem to work. I can get it to work when my field is on the checkout page but not when I pull it from the product page, perhaps I am missing a checkout process snippet?

via Chebli Mohamed