1. Form a Slab
Before beginning your slab pot, you will want to create a thick slurry. (Allow some scraps of clay to dry completely over several days, then drop them into a container with just enough water to cover them. They will quickly dissolve to create a slurry.) By using slurry instead of water, you increase the joint's strength, both in the building process and throughout the pot's life.
For small pots, you can press out slabs. Compress a lump of clay into a ball about 2 inches in diameter. Using your palms, flatten the ball as much and as evenly as possible.
Place the clay pancake on a canvas-covered work surface. Continue flattening it by pressing it against the work surface with your palm or by pounding on it. The final clay pancake should be of an even thickness, of about 1/4 to 1/2 inch. Carefully lift the slab, releasing it from your work surface.
For a larger pot, you can roll out slabs using a rolling pin.
How to score the slab when making slab-built pottery. Scoring and using slip creates stronger joints.
Photo © 2009 Beth E Peterson
Using your potter's needle, trim the slab you just created. Although you could make this practically any size or shape you'd like, for your first slab pot I recommend making your base a square of about 2 inches by 2 inches. (This does not have to be a perfect square or perfect measurements. If you can eyeball it, feel free to.)
Slightly smooth the cut edges of your square by lightly tapping each edge on your working surface. Using your potter's needle, score (or scratch) the upper surface of the slab along each edge. Your scoring should be no wider than 1/4 inch and no deeper than 1/16 inch deep.
Measure and cut slabs for a slab pot. A straight edge helps get clean cuts.
Photo © 2009 Beth E Peterson
Form a slab just as you did in Step One. Trim one edge into a straight line using your potter's needle. Laying it so it abuts one edge of your base, mark and trim away the clay so that the new slab is the same width. Trim what will be the upper edge to the height that you will want the finished pot to be.
Create a second slab and trim it to the same dimensions as the first side slab.
Attach the sides to the base of the slab pot after scoring both surfaces and slipping.
Photo © 2009 Beth E Peterson
Score the bottom edge of the side slab. On the side that will be the interior surface of the finished pot, score the interior surface along the two side edges. Using your sumi brush, lightly brush a line of slurry along the scoring on one edge on the base slab. Gently set the side slab upright into the slurried scoring.
Working at this size, the side slab should be able to hold itself upright, but in case it wants to slump you can support it with any handy object.
Roll out a tiny coil, about 1/16 inch in diameter. Position it along and into the interior corner formed between the base and side slabs. Using the rounded end of your wooden tool, lightly press and weld the coil to both the base and side slabs. Leave any remaining length of the coil attached and loose.
Repeat this step with the second side slab, making sure that you are scoring the interior surface.
Form a slab just as you did in Steps One and Three. Trim one edge into a straight line using your potter's needle. Laying it so it abuts one edge of your base, mark and trim away the clay so that the new slab will fit snugly in between the interior surfaces of the two sides already in place. Trim what will be the upper edge to the height that you will want the finished pot to be.
Create a second slab and trim in the same way.
Score the bottom and side edges of one of the side slabs. Using your sumi brush, lightly brush a line of slurry along the scoring on each edge. Gently set the side slab upright into the slot created by the first two slabs.
Position any leftover coil from attaching the first two slabs so that the coil goes up the side joint. If it isn't long enough, roll and position another length so that a coil runs the entire length of the seam between side slabs. Using the rounded end of your wooden tool and supporting the pot from the outside with one hand, lightly press and weld the coil to both side slabs. Do the same with the joints at the base and other side.
Repeat this step with the last side slab, making sure that you are scoring the interior surface.
In order to give your pot added security against cracking and breaking apart, lightly weld the outer surface of each joint, using the rounded end of the wooden tool. Gently supporting your pot at an angle to your work surface, lightly tap the bottom edges of your pot to help smooth it and create a slightly beveled slope where the pot will rest on a table. (This slight bevel gives the pot a visual lift, which is more pleasing to the eye.)
If your pot's upper edge is uneven, use your potter's needle to cut away the excess. Remember to support the pot's sides with your fingers against the pressure of the needle. Smooth the upper edge by wetting your finger tips with a bit of slurry and gently running your moistened fingertips across it. Weld and smooth each upper joint together with your fingers, being certain to support the clay with one hand as you apply pressure with the other.
Clay should not be fired until it is bone-dry. To check for this, pick up your pot and feel it all over. If it feels cool to the touch, it is not yet bone-dry. (The coolness is due to the water evaporating out of the clay body.)
Drying time varies according to the humidity of the air. Generally, a pot should dry completely in one to two weeks. If a pot is drying faster than that, cover it lightly with plastic. Drying too fast can result in the pot cracking. Be aware that greenware is very fragile; dry your pots in a place where they won't be moved about, bumped or jostled.