Feet from the front or back are difficult to draw because you see the feet ‘shortened in perspective’. Just like, for example, a horse’s head straight from the front is much more difficult than from the side. Our feet are also higher on the inside at the instep. Finally, the protruding parts of the ankle on the inside of the leg are higher.
Exercise 1: Feet from the front can be simplified somewhat by starting very lightly with a block and then drawing the curves, toes and/or shoes over it.
Feet can of course also be turned a bit, like this foot from Rembrandt’s double portrait of the couple Soolmans and Oopjen from 1634. The luxurious leather shoe, just a very small detail in the very large painting, shows the wealth of the couple. Due to the large heel, the foot is not only turned but also slightly oblique.
Exercise 2: In the following image you can see how you could draw Rembrandt’s special shoe. Start as light as possible with the block shape.