As a guy, I can personally say that I would really appreciate it if you were just honest. Like this
"hey, I just wanted to tell you that I have a really big crush on you, and I have for awhile. I really like talking with you and being friends and I really wanted to know if you wanted to take it further"
Even if it's non reciprical it will give him butterflies and make him like you more even if it's just as a friend. Only good can come from the situation.
Or you'll just end up being bf and gf