To create a layaway order, you must first add a customer to the cart.
With the addition of a customer, the layaway and store credit options will then be unlocked in the checkout screen.
At this point, you can take a partial payment from the customer or simply lay away the order in its entirety, taking no payment for the moment.
You can open this sale back up at any point from the transactions tab. The transaction will have the "lay-away: order status.
