If an order is placed that is out of stock, it will be flagged as 'stockout' in the dashboard. When clicked, there will be more details stating which action is specifically required. 

We will put the item in production as soon as it is in stock.

When we already have a restock date, it will show for you in the inventory and in the product detail pages of the respective item.

However, if you or your customer do not wish to wait, you can change color or size of the item or replace it with a similar product. It may be advisable to contact your customer to discuss product replacements.

Finally, it is also possible to simply cancel the order.