This is a surprisingly difficult puzzle for a lot of people, both to assemble and disassemble (provided you have a good friction fit between the parts). I was inspired by a similar wooden puzzle that was given to me, but that one had different types of pieces with a key block that made assembly quite easy. I realized no key was necessary, so I made this version and changed the shape slightly.
Just print six identical pieces and assemble them into a sphere as shown. I included a parametric openSCAD file so you can choose your size and change the shape if you desire. There is also an important parameter to tweak: tolerance. I needed half a millimeter to account for the inaccuracies of my TOM and allow the parts to assemble. You might have to tweak this to make sure the parts can go together, but don't spontaneously fall apart.
I changed the scad file (and corresponding stl) to do the tolerances in a more symmetric way such that the final shape is more nearly spherical. Still prints well on a stock TOM with the same tolerance value as before.