To make a box, you might fold the box like the above pictures and then glue the flaps together to form the shame of a box
But if the paper is hard enough, we don't even glue the flaps, but just tuck the flaps together.
Now I want to make a box flat.
If the box is folded and its flaps was glued, is it correct to say "unglue the box to make it flat"?
If the box is folded only without its flaps glued, is it correct to say "unfold the box to make it flat"?