The simple guideline of 2:1, upper body to lower body, from the end of Chapter 3 will help to quickly establish the proportions for this pose. The thigh and the lower leg are of the same length, so you can draw a square to roughly find the relationship of the upper leg to lower leg, when the leg is bent at a right angle.
The trick is to watch out for the subtle perspective at play—the model is seated at a three-quarter angle to the viewer, and most of the figure is situated below eye level.
purple Canson Mi-Teintes 98-lb. (160gsm)
HB, 2B, 4B and white
Draw the large squares (in perspective) first, ...