rest – How to store multiple items in a POST request?

I'm building a REST app.

j & # 39; I boxes. Each box contains goods.
Items must be saved in their own MySQL table because they will be sold separately (retail).

The problem is: the items do not have a barcode, so I save their IDs under the name automatic incrementation.

For the moment, when I put a box in a table through a TO POST request, I record the ID from the box to, as well as the number elements that it contains. When I treat this TO POST request, I loop on the number elements to create elements in the corresponding table.

It works. But it is not clean and does not respect the rest.

Please suggest me a cleaner approach.