I used four strands held together. It was a very firm fabric and took a couple trips through a hot wash cycle to felt to the size I wanted. I found this pattern to be clearly written and easy to follow. I’ve made other fulled slippers before which were very nicely shaped and excellent, but required close counting, attention, and were fiddly. I needed a simpler, faster pattern for a Christmas gift. This pattern delivered in every way. I’ll go to Monique Rae’s designs for future fulled gifts.