Answer directly: Tell him how you feel about him directly, so that he can understand your attitude towards him better. For example, you can say "I think you are interesting and smart" or "I think you are a very reliable person" and so on.

Guide the other person to answer: You can answer him with the same question, such as "What do you think of yourself?" This will help him understand your attitude towards him more clearly and help him understand himself more deeply.

Appropriate avoidance: If you don't have any special feelings for this boy, or don't want to say what you really think, you can choose appropriate avoidance. For example, you can say: "I think you are not bad" or "I don't know you very well" and so on.

In short, the way to answer this question depends on your feelings for this boy and your actual situation. Above all, be sincere and frank, and don't lie or pretend to be mysterious. ?