This will prevent the pot from draining and leaking on furniture. But beware of overwatering your plants. A tablespoon or two of water when needed is sufficient. Make a small loop in a long piece of florist wire using needle-nose pliers. Push the straight end of the wire through the plastic wrap and out of the hole in the bottom of the pot.
Spoon plaster into the plastic-lined pot until it is half full.
Pull the wire loop down into the plaster until you feel it tug against the bottom of the pot. Set this pot aside until the plaster hardens. Once the plaster has hardened, you're ready to build the legs. Repeat procedure for the other leg. Take one of the 4-inch pots, turn it upside down, and place it on a work surface.