Cart
Your hold window.
Only items in the cart should show the hold timer. If an item is already held, it stays blocked on the item page and cannot be added again until the hold expires.
Cart line items
2 itemsProduct image, title, size, price, hold countdown, remove action, and item notes will live here.
Checkout summary
Subtotal, shipping, promo codes, and checkout button.
The hold timer should stay visible here with server-based timing.