The phrase "taking a leaf out of someone's book" means learning from someone's behavior, actions, or methods. The antonyms of this phrase can vary depending on the context. For instance, if you want to convey the opposite meaning of learning from someone's behavior, you can use phrases like "ignoring their example," "acting contrary to their methods," or "disregarding their approach." Similarly, if you want to suggest that someone is being original and not copying someone else's actions, you can use antonyms like "creating a new path," "forging your own way," or "charting your course." Overall, understanding antonyms for common phrases like this can add nuance and help you express your ideas more clearly.