From a teacher's perspective, let me encourage you not to overthink this assignment. More than likely, your teacher is expecting you to think outside the box, show some creativity, and put some of yourself into this project. If I had given this assignment, or were completing it myself, I'd probably follow these steps.
Before you do anything, if there is a provided grading rubric (list of expectations or necessary components), familiarize yourself with it so you know if there is anything you mustinclude.
Next, choose your character. Sometimes, it is easier to find interesting qualities and characteristics of an antagonist over a protagonist. Keep that in mind.
Write out a descriptive list of this character's qualities. This is where direct and indirect characterization comes in (likely part of the point of this lesson). Think of physical description, the character's thoughts, dialogue, actions, and the reactions of others to the character.
Finally, get creative.
I'll give you a number of suggestions that would more than meet my expectations as a teacher: a collage using pictures and words, a physical drawing including details, a three dimensional representation that may or may not actually take on the form of a human, or something that also incorporates other aspects of the book.
Basically, you want to show your teacher what you know and understand about this character. The more creative you can be, the better, but do not forget to add substance in addition to art. Have fun with this, and good luck.