The simplest way is to ask, "Can I talk with you about something please?" (So he knows you’re serious and he has to pay attention.) Then say, "I really like you. Is that a problem for us?"
You can’t be positive what he’ll say, so be prepared for a further discussion that could go either way. Just in case he’s never considered dating you and is uncomfortable with the idea, be ready to deal with that.
You might need to say something like, "That’s okay, I’ll get over you. We can be just friends if that’s how it has to be."
Or if you really can’t stand the thought of him dating other girls in the future, and you don’t want to be his friend and to have to be nice to them, it might be time to start putting more distance between you and finding other friends.
But if you believe there’s real chemistry between you, give it a try. It would be a shame not to try being a couple just because you were both too afraid to raise the subject.