According to the book the first step is to draw a circle big enough to contain the skeleton. The circle has to be perfect and drawn with my blood, and the lines have to be thick enough to contain the power needed. To be honest this takes me longer than I like to admit, drawing a perfect circle is hard.
When I finally do draw one perfectly I then find it isn't big enough to lay the skeleton out inside it so I have to start over. Several times during this I have to stop and eat and rest because I have lost too much blood. Yet I can't just drain my blood into a container and then draw it because once it starts to clot the lines won't be even.
So I keep cutting my palm repeatedly and trying to draw the circle like a kid playing with crayons. Eventually I wise up and cut a circle in the floor with Blitz, once it is right I then trace over it with blood. That works much better and I manage to complete the circle finally.