1. The tip of a pair of scissors is inserted and cut around the rubber. (Image 1)

2. Put the rubber on the bottom, to cut straight, and cut equal strips from top to bottom. We can make them wider or narrower, as we like. (Image 2 and 3)

3. We throw down the strips that we have cut. (Image 4)

4. Going over the next one, we take the strip to put it under the next one, glued to the edge of the circle. Thus, until reaching the last one, which is tucked under the next one. (Image 5 and 6)

I leave you this tutorial from Facilisimo.com, which explains it step by step: