Make a hollow ball for the pig's body. The easiest way to do this is a method called "pinch potting." Start with a large ball of clay, and make sure to knead it very well against the table to release any air bubbles that may be trapped. Once your ball is nice and round, stick a finger into the center; this will be the beginning of your bowl. Hold your ball in one hand very gently, cupping it with your fingers, and use your other thumb to pinch the clay out, creating a bowl shape, always starting from the bottom, thickest areas. Continue until you have a nice, round bowl shape approximately half the size you would like your piggy's body.
Create another bowl the same size. Don't worry if they don't come out identical; just make sure their lips (the tops of the bowls) are very close in size. When you are satisfied, take your toothbrush and score (scrape across to create texture) the two lips. Clay must always be joined this way to create a lasting seal. Brush your slip over the areas you have scored, and join the two sides together so that they are airtight. Roll, paddle and smooth the belly you have made. If you like, make it into an oval, but for a nice fat pig, round is perfect, and easier.
Build piggy's legs with the same method. Create four small pinch pots of equal size and attach to the bottom of his body by scoring the lip of each leg as well as the spot on the body you will be attaching to. Don't make any of these pots much thinner than ¼ inch, or they may collapse under a load of heavy coins. If at any time you need to take a break, just make sure all the pieces you have sculpted so far are placed under some plastic wrap to be kept from drying. Use slip if your pieces do not seem to be attaching correctly.
Make piggy some features. Here's where it gets fun. Sculpt your little guy a nose, ears, eyes. You can use two small balls of clay for eyes. To make a tail, roll a ball of clay out on the table into a snake-like shape with your fingers, than twist very gently, creating the perfect little curl. If you prefer, you can simply carve piggy's features into his body.
Cut your coin slot. To do this, allow your new piggy to dry until he is leather hard. Use your very sharp knife to cut the coin slot. Remember that clay always shrinks a bit during firing, so make the slot slightly larger than you need.
Use the pin tool to poke a hole in each leg in a hidden place, such as on the bottom. If you do not do this, the air trapped inside will heat in the kiln, and your pig will explode. Make sure the pin goes all the way through the clay, and that you have created a hole that won't close in on itself.
Check your piggy for any other changes you might want to make now, and remove excess clay with the pin tool and sponge. Don't forget to carve in some initials or a dedication at this point if you'd like them; otherwise you will can paint it on later. Let your piggy dry up to a week before bisque firing.
Fire the piggy once (bisque firing) and then again (glaze firing). Before glaze firing, be sure to glaze or paint your piggy, if desired. If you want to keep the natural clay look, seal with a clear glaze or other means. If you do not have access to a kiln, you should be able to find a local ceramics shop that will fire your piggy for you.