Make a strip (like 4 sheets thick) same length as the outer circumference of your ring.
Make a circle (like 4 sheets thick too) of 4 cm diameter.
Bent and stick the strip to the circle with more paper.
In order to get a thicker face, place some yarn soaked in glue around the circle.
Paste another circle on the top. Let it dry.
Cover the ring completely with tissue paper and glue. Let it dry again and then you'll have an even surface to work with. Now you can paint and decorate it. :D