Stacking Wall Pocket - The tiny cup shelf for tight bathrooms

These tiny angled high-walled shelves are built to link into each other so minimal mounting hardware can connect them to the wall and add together for greater strength. Each one has a single screw at the top but links into the shelf above it. There is no theoretical limit to the stack height. The bottom is open so any moisture should quickly clear. 

Printing: 0.3mm with no supports on a Prusa MK3+, bargain basement PLA. Bottom of the cup (the hex pattern) goes on the plate for me. If your printer can't handle bridging well or for some other filaments you might want to add something to support the reinforcing bridge halfway up the cup.