I've designed this soapbox to be in the shower with a lid so water doesn't get in it, and it has holes on the bottom so if any water that does get in when you're using the soap and leave the lid open, doesn't stay in. It also has longitudinal bumps across it so the soap doesn't get stuck,
The size is made for most conventional soaps with some margin around so it's easy to get you fingers around to pull it out.
The lid pivots to open and close and doesn't click in, it sits on top of the box, allowing for easier one handed operation, and the edges go around the box a few milimeters so water doesn't get in..
Should work with any filament. I like to print the box itself in PLA for easy printing and more colour selection as welll as rigidity, and the lid in PETG so it's easy to mount in on the pivots from the box. If it's too stiff it's hard to click it into place and you probably can only do it once while with PETG it's easy enough with the extra flex. Still, it's OK to print it all on the same filament and so I've included the 3mf file with both parts in it.