The crotch area of the bottoms will be made with a chaining stitch.

chaining

1. Get your hands in a comfortable position. Twist your needle counterclockwise around the front of your working yarn and bring the yarn down around your needle.
   

2. Twist your needle so that you grip the yarn with the hook and pull the hook and yarn through your slipknot. Don't pull too tightly. You'll be coming back through these stitches.
   

You've made your first chain! Whew! Now go take a water break! When you come back repeat this until you've made a chain that's the right width to fit between your thighs, about fifteen-twenty chains.