Things You'll Need
Instructions
Build a small box using cardboard and tape, of the approximate size you want the gelatinous cube to be; a 2-inch square is suitable for most Dungeons & Dragons maps. One side of the box should be open. This is the mold for your gelatinous cube.
Place the plastic wrap into the mold, spreading it out so it roughly conforms to the square sides of the box.
Spray mold release agent into the mold, making sure the surface of the plastic wrap inside the mold is coated.
Mix a small amount of clear resin with hardener as described on the package.
Pour the resin into the mold. Be sure to pour slowly to reduce the number of air bubbles in the resin.
Allow the resin to dry as recommended on the resin package.
Remove the hardened resin from the mold. The release agent will allow it to come out easily, and the texture of the plastic wrap will have created a flowing, watery surface to the cube.