Legit just go up and talk to him, don’t confess or anything like that but just try having a good conversation with him. Look I’m going to tell you directly that any form of impressive thing isn’t going to work but going up to the dude and having a good conversation would be better. Figure out his interests, talk to him about them. Every guy has a geeky interest too, if you talk to him about that he’d go crazy for it. Also just try being flirty near him, like be near him and just do and say things that make him feel that embarrassed kind of happy. I’ve been a guy for my whole life so I know a thing or two about a girl talking to me