Definitely flirt with him. Flirting is the way you can show him, without telling him, that you’re interested. It’s a lot less awkward than telling him because it’s lighter. It’s all about smiling at him (a lot), laughing at his jokes, complimenting him, asking him questions about things — and basically showing him that you’re interested and you think he’s great. He’ll notice you, believe me! If he’s interested, he’ll respond with interest and even mutual flirting. Then, the ball’s in his court to invite you to do something together.
Hope that helps! 🙂