Take the sturdy piece of black cardboard and cut out a 12-inch by 12-inch piece. Put aside and save for later.
Take the white clay and, using a plastic knife, cut a piece the length of the clay block. Lay this piece of clay down and begin to roll it, so that it creates a long skinny stick (pencil thick) about 10 inches long. Make eight long sticks of white clay, all 10 inches long. Using a cookie sheet underneath, assemble the sticks into a square, using four clay sticks for the outside. Then place two of the sticks horizontal inside your square about 3 inches apart. Then take the last two clay sticks and place them horizontal about 3 inches apart. When you're finished you will have a box with nine squares. Where the sticks meet, simply squish together to give a seamless look, while the clay is still moist. Set the cookie sheet aside.
Using the red clay, cut off about 1 inch of clay and roll it out with your fingers, using a back-and-forth motion. Once it is rolled out in a long stick, cut that stick in half. Then place one stick over the other to make an X. Repeat this process and make five Xs.
Take the blue clay and cut off about 1 inch of clay and roll in a ball in your hand. Then slap the clay on the table, making the bottom of it flat. Next take your pencil and use the eraser end to punch a hole in the middle of the clay circle and discard the middle. Repeat this process and make five Os.
Carefully place all your clay pieces, on a cookie sheet and bake in the oven. Let cool.
Take the piece of sturdy black cardboard and arrange the square boxes so that it is centered on the board. Glue the bottom side of the clay square to the board.
Once the board is dry, it is now time to play pottery tic tac toe.