Make scratchboard out of an old CD. Paint CD with 3-4 coats of matte black acrylic paint. shade piece of paper with pencil as shown. Place paper pencil side down onto painted CD. Next place pic of your design on top and trace firmly. This will transfer the image onto the paint as shown. Slowly scratch out your design with a scratch knife, or in this case, a clay tool
Creating mandalas and recycling CDs, step by step - Mandala Morocco by Mary Taveiros @ viladoartesao.com.br - with instructions. Page is in Portuguese so I did a right-click and selected "translate this page"