Feet from the front or back are difficult to draw because you see the feet ‘shortened in perspective’ (= not in their full length). 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, a detail from Rembrandt’s double portrait of the couple Soolmans and Oopjen from 1634. The very luxurious leather shoe shows the wealth of the portraited couple. Due to the high heel, the foot is not only turned but also slightly oblique.
Exercise 2: the following image shows a simplified way to draw this special shoe. Start light so you can easily erase lines if needed.