How do I create a flattened container clone?

Say, I have a layered cake of containers: container0 which has some base stuff, then I lxc-copy -s it to container1, add more things on top, lxc-copy -s that to container2, do some final configuration. At the end I want to produce a container3 which would be a standalone copy of container2 squashed together, without any reliance on container1 and container0. How do I do that?

I understand that a regular lxc-copy (with no -s) will preserve any snapshot information already existing in the original.

Oh, also: I’m using the unsophisticated setup where the backend is dir and snapshotting is done using overlayfs.