I just searched for your post, very nice! (Box with a Laser Tile Lid).
I like the box idea a lot. I originally had something similar as your lid where the back piece was sunken in / not flush, but I wanted to mount these flat on the wall. I’ve always been a fan of when art can hang perfectly flush with the wall, no gap at the top, so I figured this way I could have a screw head sticking out just the right depth to create a flush piece. Especially when the plan is to have nine of them, I think it would look best.
Your box makes a great gift idea, I would make one and then line the inside.