This has now officially become an obsession, the quest to create the perfect Gelatinous Cube. Here is the latest effort:
As you can see this Mark II cube is somewhat larger than his Mark I brethren, hence the use of a Dwarven Forge corridor to house him. I'm getting there quietly I think; this version is nearer to the 10x10x10' cube described in the Moldvay Basic D&D rulebook and the sheer size gives it some impact compared with my earlier ice cube efforts. I'm still not happy with the finish though, the current batch of clear resin doesn't seem to de-gas as well as it might leading to the slightly 'fizzy' look; also this disguises somewhat the old helmet and coins held within, which again have settled to close to the surfaces to look right.
Hopefully Mark III will be better, back to the drawing board!