You will need:
-some round shaped things like tins or jars (10 cm is great and you will also need a smaller one)
Cut round shapes from cardboard. Diameter of 10 cm is good. Choose some magazines or print anything you like and use those for covering the cardboard circle. You can see the technique for this in the pictures. Cut smaller circle from printer paper or magazine and glue it in the bottom of the coaster. Now it's ready to use!