Not much way to make a low-cost mode except with plaster of paris (or similar material) and it will always be two-piece. But, then, professional molds are two-piece, in that they pull apart to eject the molded bodies. Even those with 200-300 cavities. Just get a spray can of Pam, or such, and lubricate the inside walls and cavities of your mold each time so nothing sticks together. A nice thing about the plaster is that you can take an Exacto knife and customize your mold with small details. HOWEVER, you can have a one-piece mold if you will accept a flat side on one part of your poured lure. Many bass folks do that with worms and 'creatures. Sure is a lot easier and quicker and I truly don't think fish are smart enough to care.