If you mean like this:
http://www.coolminiornot.com/pics/pics13/img488d618269d62.jpg
Then prehaps, but you would only manage to get it about 2mm deep and there would be no point in building up a box for the casting.
The best way to do it is with the two part epoxy resin, such as envriotex lite, just make sure that it is a clear setting one, which wont react to uv light.
As long as you follow akaranseths guide, you should be alright, its one of the best out there. Just remember to READ THE INTSTRUCTIONS on the resin, because each brand is differnent.
Alex