1. Cut a circle out of your 3mm (0.12 inch) thick felt. The largest circle should be made with your 3mm (0.12 inch) thick felt. This will be the base of the coaster and will dictate how large or small the coasters are. Typically, the largest mugs are 4 inches (101.6 mm) wide, so you're going to want to make your coaster at least 4 inches (101.6 mm) in diameter.
If you are having trouble cutting circles, you can purchase stencils that can help you
2.Cut smaller circles out of two different colors of felt. Take your thinner, 1.5 mm (.06 in) thick felt and cut a smaller circle from one color of felt. Once you're done, take a different colored piece of felt and cut an even smaller circle. These felt pieces will layer on top of one another to create the design for your coaster.
3. Stack the circles on top of one another. Stack the circles on top of one another, with the largest circle being on the bottom. Arrange them however you want, whether that be centered or asymmetric. Once you're happy with how you've arranged them, you can get ready to sew them together.
4. Sew the circles together. The goal is to make the stitches look random, so your only goal is to make sure that the circles are tightly fastened to one another. Sew in a circle, starting from the second largest circle and go around multiple times. Continue to work your way closer into the center of your coaster until all three pieces are sewn together.
When you're done sewing the circles together cut off the excess string.
Precision is not required for this step.
If you don't have a sewing machine you could stitch the circles together by hand, but it will take much longer.
5.Done! You can now use your colorful stacked felt coasters