Stolen Death Star plans (ice "cube" mould)

I tried some of the ice moulds for a death star, and the problem is they leak, and so you end up with half a death star and a puddle of ice in your freezer.

So I have made this one so the base can be printed water tight and the top slotted in to it, then, when frozen, you can remove from the mould.

Tried with ice - was rather too stuck to the material (nGen flex). I suspect it may be easier with jelly.