The first step in making a Sawtooth Star is making 4 "Flying Geese" blocks which will eventually be the points of the star.
This is a Flying Geese block, by the way.
To begin, I used a tool called a Hera Marker to crease each yellow square diagonally from corner to corner. It's a knife-shaped piece of hard plastic that marks your fabric without using ink. You use it like a fabric pen. I think it's based on a really old tool made out of whale bone.