First, I laid the quilt on the floor and put something hard underneath it (in my case it was an 18-inch square of the stuff that clipboards are made of -- that's just what I happened to have).
Then I lined up my template (which I made out of cardboard -- you can buy templates already made, but a lot of times it's just as easy to make your own).
Then I took the template off and filled in any gaps.
First fan marking completed.
Next I lined my template up against the just-finished markings and repeated the process, making sure the hard surface underneath the quilt was lined up with where I was marking.
Another fan completed.