So I'm kind of Jello crazy and have begun a series of craft experiments utilizing it. This is the second experiment(the first was gummi venus de milo replicas).
What I was trying to do was create edible faux stained glass. So I made me a squid. First I poured red Jello into a cookie pan and let it set up. Then I cut a squid shape out using a butter knife. I carefully removed the extra Jello. I put the squid in the freezer while I made blue Jello. Keeping the first part cold is really important or the second batch of Jello will melt your pieces. I poured the blue Jello carefully at each corner of the pan and used the knife to scoot Jello into areas that it didn't flow easily into, like lines between parts. I then let this set up.
Unfortunately I should have used some kind of cooking spray because even though the surface was non stick my Jello did not want to come off without a fight. I could get small sections off, but not the whole thing in one piece. Also, make sure you don't our any unmelted sugar in the bottom of your melted Jello container into your finished piece. It makes it slimy and grainy and your material will simply fall apart in those areas.
If I had made my Jello thicker(the layer was about a centimeter in the pan) and used a release agent(like cooking spray) I bet it would have popped out of the pan just fine. I did try flipping the pan over and banging on the backside, but it wouldn't budge.