For the size I want to print, a pure cube won't cut it, but I did manage to make a form-fitting mold by making the cube hollow, then removing the cube proper, being left with the mold proper.

I've been spending quite some time trying to figure how to properly cut the mold into 2 or 3 parts in a way that I can actually close the thing and pull out the cured silicone without it deciding it'd rather stick to the cured resin. I've given some thought on making a single use mold, but I also gotta figure how to ensure its interior gets enough release agent to help me demold.