These boses are stackable, even the cover. There are built-in slots to partition the box.

The boxes measured 240x200x40. I use these boxes to keep some of the prints I make, it's good for tidying up.

The cover measured 240x200x14. It's a bit shallow, but it's also usable as a shallow box if you want to keep something thin.

Support is required for printing because of the stackable area, though there's some cleaning up to do after removing the support to ensure even fitting.

Let me know if you think a different height is useful. Open to adding more height.