A cube for keeping camera battery neatly stored. I've created an openscad of the battery, and subtracted that a filled in gridfinity cube. At the bottom there is a compartment to put some weight in. (it is 7.5mm high, so don't put anything tall there. A rusty nut, or a wheel balancing weight I found on the side of the road.

There was some funkiness with the scad/stl of the battery, so I'm enclosing the 3mf file.