This is how I spent biology class, lol... I could afford to not pay attention because I knew enough about what we were talking about that I could TEACH the class, lol. So, I sat and doodled while listening to the lecture and looking over the slides he pulled up and illustrations on the board so that I would still know what was going on... but, yeah.
this was all free hand with a blank sheet of paper and black gel ink pen. No reference, no sketch, not trace... A little proud of myself.