The mold is now prepared for creation of the core. The core will be made out of Smooth-Cast® 320 resin with Ure-Fil® 3 added to reduce cost. Lay a 1/2” thick layer of clay into each half of the mold. Then, bolt the mold closed with the clay inside and place in a container and level. Drill registration notches around the edge using a countersink bit. Next, build a clay wall to contain the Smooth-Cast 320 liquid plastic. Spray both the interior and exterior surfaces with Universal Mold Release.