I will add more details of the pattern later but basically you knit 1 inch on circs as if to start a very simple hat. Then you pick up 8 stitches at a time and knit vertically to add the panels. You need to join the panels as you go which, to begin with, is pretty tricky, but not hard to pick up and remember.
It was a surprisingly fast knit too. It took me 3 days of knitting on and off when my son was asleep or otherwise occupied.