Either
A: Ask him directly (make it a lowkey thing like if he flirts a little be like "Dude, do you like me?" Or smth IDFK BOYS DON'T LIKE ME (actually they do, but they're all gay in the end

i love my gay lovers)
B: Try and flirt with him too, if he sees your interested, he could be more inclined to opening up to you and HENCE giving the "sooo umm I'm into you"
C: Or you can watch his poor puppy love spiral until he's asking you out without much effort
Hope this helps!! (I'm straight, dawg trust)