To do so evenly roll out your clay to the thickness you desire using rolling clay slab sticks 3 8 inch is a good starting point.
Compressing a slab ceramics.
If the clay it is too thick it will not fit under the roller.
I have been making slab platters for years by slab rolling a large piece of clay draping it over my bisqued hump mold which i made years ago.
The second type of mold is a bisque mold which is super easy to make yourself.
When the foot is finished trim the excess slab to about inch away from the rim of the bisque mold 13 and compress this clay into a nice rounded edge above where the clay meets the bat.
Use a template or a bat to cut a circle out of the slab.
Then take a straight needle tool and holding it flat against the bat surface press inward until the needle tool can be felt dragging on the bisque mold.
Preparing and compressing the slab.
Before you use the slab roller make sure that the clay slab is no more than three or four times thicker than the desired result.
Start by rolling a basic slab 12 14 inches in diameter and 3 8 inch thick.
Drape it over an inverted footless bowl that was bisque fired to two or three cones lower than the clay body s maturity see 1.
Then i use a large window squeegee to compress starting from the far side of the foot area and pressing it into the clay while i draw it toward me.
Then cast your mold to form the shape of anything from cake tins to plates.