This works up really quickly but can get a bit fiddly around the legs. I've included as many diagrams and images as I could to hopefully make it clear.
I only started this crochet lark a couple of years ago now and since learning the basics have been totally unable to follow a pattern. So, I just make up my own and occasionally - I write them down. :)
I have two children at school, my daughter is totally the reason I keep creating these things!