First I started out with a piece of paper. I cut to match the tarp so a 8'x10' tarp = a 8"x10" paper
I marked the paper with a Sharpie where the grommets are.
Since I didn't want to add grommets I cut it on the dot in the boxes that are on the picture and made a triangle.
Then I folded the paper in half.
This is the model I went off of.