The settings are under WooCommerce, Settings, Box builder.


Block and shortcode
Add the Build Your Own Box block to any page and choose the box in its settings, or use [wfbb_box id="123"]. On a box product page the builder appears by itself.
For theme developers
Copy templates/box-builder/builder.php and item-card.php to yourtheme/woocommerce/box-builder/. Colors use the CSS variables --wfbb-accent and --wfbb-track.