Compress a wad of clay into a ball. Flatten the ball on a canvas working surface, making the thickness as even as possible. This wafer should be about 1/4 to 3/8 of an inch thick. Trim away the outer edges, using your potter's needle or wooden trimming tool. For your first coiled pot, I recommend you work with a bottom that is no more than 2 to 2 1/2 inches in diameter.
Carefully lift your pot's bottom in order to release it from your working surface. Smooth the edges by lightly rolling it, as if it were a wheel, on your working surface.