Slab pots are made by hand-building pottery techniques. Hand-building pottery allows the creation of shapes beyond what is possible with potter's wheel. Slab pots are usually shaped as squares and rectangles. Since clay is used in making slab pots, you don't need to keep water away during the construction since moisture strengthens clay. Making slab pots is a straightforward pottery process and you should be prepared to use your hands in rolling and shaping the clay.
Cover your flat work surface with a spread of cloth. Place a lump of clay on the cloth. Spread the clay out by flattening it with the palm of your hand. Make sure the flattened clay has a thickness less than ½-inch.
Hold the clay by the top and bottom. Flip it over on its other face. Place a yard stick on each side of the flat clay. Roll a rolling pin back and forth repeatedly over the surface of the clay until the surface becomes smooth and even.
Place a ruler on the face of the clay to a side. Cut the length of the bottom of the slab pot with a knife. Place the ruler perpendicular to the first cut and cut the length of the breadth of the bottom of the pot. Complete the other two sides of the bottom the same way.
Repeat Step 3 for the four sides of the slab pots, taking care to cut out rectangles of the same size. Allow one hour for the four pieces of clay to dry.
Scratch crisscross patterns on the faces of the clay pieces at the edges with a potter's needle. This will help create stronger joints.
Put scraps of clay left from the cutting into a small plastic cup and add a little water to it. The clay will dissolve into slurry to make the slip. Apply the slip to the scratched areas with an artist's brush.
Stand each of the sides straight and slide it over the scratched edges of the bottom at a right angle. Slide each side of clay block back and forth on the bottom piece to strengthen the bond between the surfaces. Press a coil into the seam of each corner as soon as it is made. Use the brush to even out the corner over the coil.
Smooth out the corners of the slab pot with a damp brush. Even out the top edges of the pot with wet paper towel. Let the pot dry for two days.