My household needed a wall-mounted pocket to store mobile phones (which are not permitted in the restroom). I made this to fit a phone and case with dimension 90mm x 20mm. I made the height 100mm as the max height of my build space, so most phones should fit. This thing has holes in the bottom for drainage and/or to prevent items from getting stuck. It does not have any mounting holes, because we used adhesive strips to mount it to the wall.

50% infill makes it super sturdy; you can surely cut that back.
The corners are filleted so a couple of brim lines can help this adhere; my bed isn't heated and printing upright without supports, it stuck fine with some blue tape and hairspray.

Wanhao i3 mini

No

50