I took a portrait drawing class.
Everything is made from the box.Everything.
So,Once I start to draw human face,I try to see the face as a box.
It is not difficult,but it's not easy.
First of all,I made a big one box.And I made hair,eyes,nose,mouth,ear....boxes.

Second step is that breaking the box and making geometric shape like triangle at each part.

Do you know that every part has a plane?Not only making a box but also making a plane.Look at around cheek
.You can realize which part is come out or hollow.

Break down the hair.In fact, hair is gathered many lines.But I also saw hair as a box.And break it down.

I put shadow to make illusion.



The most important thing is how you understand.