This design was one I came up with after I downloaded a free treasure chest cut file and was disappointed with how flimsy and weak it was. Also on the way the supports and hardware hung out from the box and can get caught on stuff. So after a few tries I made this. The other design constraint is 6”x4” internal area so it can fit note cards, or photo prints. Was thinking of marketing them as treasured recipes box and as treasured memories boxes.

It uses pieces sandwiched between the 2 layers of 3mm to create reinforcing links between the lid slats as well as form the hinge; all in the 2 layers (6mm/~1/4”) wall thickness. Plus side it adds a good amount of strength. Down side is pieces are fiddley and tedious to assemble. Also they are just finger joints plus for the joinery and failed the stress tests.

The actual flaw - you have to keep it perfectly square while gluing up because if a twist cures in place - and the lid doesn’t line up with the box… it will never line up with the box. So the possibility of selling this version as a kit would mean it’s a very high difficulty kit and the possibility of users being disgruntled if they rolled a 1.

I have plans for a new version of this using my much better locking hook joinery along with much thicker walls. I found the design is very self squaring. Then for the final touch I want to use a miter cornered hardwood skin made of 3mm thick re-sawn sheets that are completely solid and cover all the internal joinery.