The easiest a way to make a dish.

Put some of the clay on the table.
Put the clay with your palm to pat it moderately flat.

Put two thin wooden boards of the same thickness on both sides of the clay.
And put rolling pin on that.

Roll the stick on the clay until the clay becomes the same thickness with the wooden boards.

This is the plaster mold.
Put the clay on the mold.
Make the shape along it.
Leave it there for several minutes to dry it moderately.

Several minutes later, turn it over.
Take the mold off the clay.
You can adjust the shape that you want to make.
It's all done. Shall we make it ?