To create a placeholder for a bezel set stone, create a bezel around your chosen stone. Fuse the seam with a torch. Test fit the stone to be sure that it fits well. It should be snug, but come out of the bezel easily. It should not be so loose that you can see gaps around the stone. The bezel can be pressed into the clay (careful not to go too deep or it will tear during firing, use at least a 5 card slab for a pressed in bezel), or set the bezel on the clay and add a rope of or syringe around the bezel to lock it in. Cut away most of the clay inside the bezel except enough to leave a ledge behind the setting so the stone does not fall through. Press the stone back into the setting carefully (so you don't damage your work). Let the clay dry to leatherhard with the stone in place. When dry, remove the stone by pressing it out from behind very carefully with a skewer or something that won't damage the stone, or better yet, use a wax stick to lift the stone from the front. Mix enough investment to fill the cavity and pour investment into the cavity. Allow to dry completely. Fire. After metal has cooled, dissolve investment in water. Finish all polishing and patina operations and then set the stone. Makes a perfect seat everytime.