The first task I would suggest you need to think about is to pick a time in the novel when you are going to write your monologue. Are you going to write it looking back at the end on all that has happened, or are you going to pick a major event in the novel and write your monologue straight after that, giving Bear's view of it? One section of the novel that would be a good choice would be when Bear meets Crispin for the first time. Writing a monologue that gives Bear's perspective on what happened and how they met would be a very good exercise, as it would enable you to explore the difference in the perception between Crispin and Bear. If you look at Chapter 12, for example, it is clear that Crispin feels terrified by Bear when they first meet. Note how Crispin reports what Bear says and what he does to him:
"Bread is never free, boy," he roared. He was still upon the ground, but his arms were long and his huge hand held me fast while the bells of his hat tinkled with the force of his exertion.
Crispin's account is dominated by the size and greater strength of Bear. To retell the same incident in a monologue from Bear's perspective would be to explore Bear's feelings of having a small boy try to rob him and how he dealt with it. It would be interesting to chart not only what Bear does, but what he thinks when he first confronts Crispin and then how this changes as he realises Crispin has been declared a wolf's head. Will he feel sympathy for Crispin, or will he feel suspicious? You will need to answer these questions in order to write the monologue well. Remember, you can add what you think Bear will think and feel at various points, though of course you will need to keep the same words that he says to Crispin. Good luck!