c.) Pipe cleaner shaped into a loop - this option is best if the first two described above are too wide for your clay charm. Start out with a short piece of pipe cleaner or craft wire. Make a small loop on one end. Insert the straight end into the clay. Push carefully until only the loop juts out of the clay. Pat the clay around the loop.
Make details with more clay. You can decorate the edges, write an initial or name at the center, or fill the center with clay formed into flowers, hearts or any other design you like.
You can use the set of plastic tools that usually go with the clay or use small plastic spoons, knives or toothpicks.