Rectangular casseroles suitable for baking brownies and lasagna, can easily be fashioned by wheel throwing two sections.
Not all claybodies are suitable for use in the oven because they cannot withstand the thermal shock of heating and cooling in a kitchen.
The slab for the bottom is thrown the night before the slab for the top is made, to give it time to stiffen up.
A bat, rather than bare wheelhead, is used.
To make a 16" diameter slab, use a little over 5 lbs of clay.
Then take the bat from the wheelhead, and let the slab dry.
The slab for the top is thrown from 5 lbs of clay, which is centered on the clay potter wheel and formed into a low, wide cylinder 14 inches wide and 3 inches high.
This makes for a thick rim at the top which protects the finished casserole from chipping and cracking.
When the top has been thrown it is left to stiffen a bit, so that it feels tacky, but is firm enough not to slump when it is shaped.
Cut the bottom out, and slowly pull and shape opposite sides of the cylinder to form a rectangle.
Take as your length 15% longer than the length of a lasagna noodle, since the shrinkage from wet stage to fired piece can be from 10 to 15%.
Before the top stiffens, square up the sides using a ruler.
Excess clay is shaved away using a wooden rib, to leave a half-inch lip around the inside.
This lip inside the bottom makes it possible to attach the bottom section to the top without a coil.
When the rectangle is leather-hard, it is placed on top of the base slab.
The inside edge is traced onto the bottom; and then it is cut around the outside edge with a fettling knife.
The bottom is then separated from the bat.
The marked outside edge is scored and slip is applied to it.
Then the top is placed back onto the bottom, and aligned.
The outside edge is smoothed with a sponge and rubber spatula until they are joined seamlessly.
Placing a bat on top, the casserole is then flipped upside down.
With a metal and rubber rib, the join is smoothed out.
The bottom edge is beveled with a vegetable peeler, and smoothed with a damp sponge.
The casserole is flipped back over and the handles are attached.
These should not extend too far out, or else they will be likely to crack since they heat and cool faster than the rest of the casserole.
Handles can be pulled and bent into horseshoe shapes.
Handles are attached by wetting them with slip and pressing them firmly into the sides of the casserole.
The piece is allowed to dry slowly, and is decorated with cone 10 glazes before being bisque-fired and glaze fired.