GREEN LIGHT: How do I let a dense guy know I'm interested?

I try to talk and hang out with my crush whenever I can, but my friends tell me he'll never construe it as me flirting with him since I'm generally friendly with most people, and he's also quite dense. It's true, I am quite extroverted with other people- guys and girls alike. But I'm not much of an outright flirt either. What's a big enough clue I can drop without having to rip his shirt off him?
GREEN LIGHT: How do I let a dense guy know I'm interested?
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