Most commonly made of clay, like regular molds.
Circular Ring is the most common style. Comes in 5", 7", 9" or 11"
diameters. Most are smooth, some are textured. Could create your own
with Kaiser Lee Board or fibreboard.
Fuse your project normally first, sized to outer measurements of mold. Can do a tack fuse/slump in 1 firing if you want to.
Place fused project on top of drop ring, and place some
shelf paper directly underneath drop ring's hole. You could use Lava
Cloth or fibr...