As you hold the clay sphere, press your thumb into the center of the ball, about halfway down to the bottom.
Shape a piece of clay into a smooth ball about the size of your hand. As you hold the clay sphere, press your thumb into the center of the ball, about halfway down to the bottom. As you revolve the ball with one hand, press the walls out evenly with your thumb on the inside and your fingers on the outside. Smooth the surface with a damp sponge.