Right, but the point is a btrfs snapshot does that for you. No need for a "flattening" step, just make a copy-on-write snapshot of your layer at whatever state

Right, but the point is a btrfs snapshot does that for you. No need for a "flattening" step, just make a copy-on-write snapshot of your layer at whatever state it exists in and go. Delete the original later, etc... Doesn't matter.