This is a challenging pose for the model and for the artist because the angles of her head is very tilted. It's important to draw the placement lines in right away in order to keep the face symmetrical. Still, it's not easy to KEEP it symmetrical, as I found out when I attempted this piece. As for the model, she had a difficult job. Her hand fell asleep and if she moved even slightly the lighting changed, poor thing.
I was happy with the final result, which shows a slightly sleepy yet beautiful young woman, but it was one of the more difficult alla prima pieces I have ever painted.