As a little tip for making jaws and heads on a Stickfigure, don’t be afraid to make it much smaller because once you add a jaw in the shape will come together and you’ll be glad you made that move. For female characters you’re alright to make the head bigger or more rounder ( less shape to the jaw ) as they have rounder faces and heads.

As for the eyes, mouth, nose etc use a little line of reference to establish the angling and where everything should be.

Look at reference pictures and keep in mind what angle you’re going for, mixing two accidentally can look very off.