Soften a large quantity of clay to use as a base. You can make whatever color you want.
Then, soften small quantities of 4-5 complementary colors which can go well with the base color. In my case I used a soft pink as a base and then I added navy blue, pale yellow, red, orange, pale blue and eggshell white as complementary colors.
With a rolling pin or a pasta machine, roll the base color until it's about 5 mm thick (3/16").
Now roll all the other colors as thin as possible. Then with a precision knife or a utility knife, cut teeny tiny pieces of each color. Try to keep a geometric shape to the pieces.
With the knife or with a toothpick, place the small colorful pieces randomly on the base color. Do not overfill it, the base color should still be visibile.
When you're done, with the rolling pin or a pasta machine, roll the clay until the surface is smooth and even. Do not make it thinner than 3 mm (⅛").
Now with the precision knife or metal cutters (even cookie cutters if you find small ones), cut out the shapes you want. Make a hole with a toothpick to attach the findings.
Carefully transfer the pieces to parchment paper and bake in a preheated oven at 110°C (230°F) for about 30 minutes.
Once they're cool they're ready to be mounted as jewelry. You can also use an apposite glaze if you want them shiny.