Summarize the following:
Eyeballing it is fine; you don't have to use a surface. Rest the scarf over your chest. It should be about evenly centered. They should wrap around your neck and come back in front of you.  Tie the points in a knot as loosely or tightly as you see fit. Leave the knot exposed or place it underneath the other layer of the scarf. If you do choose the leave the knot exposed, experiment adjusting it to the right or left for a more asymmetrical look. Your scarf should be fairly malleable and sit in a position of your choosing. Depending on the size of your scarf, play with the length of the two layers. The knot could hang at the top of your neck or underneath, creating automatic volume.

Summary:
Fold your scarf into a triangle. Grab both points and bring them around to your front. Fluff away!