I don’t know how to flirt! Can anyone help?

I’m (F) conversing with a mate (M) right now from uni and he occasionally makes a flirty comment within our conversations. I’m pretty sure he possesses some sort of feelings for me as a result. I want to do the same but I am unsure of how to properly flirt with someone else (especially over text).

Also I’m not interested in flat out saying “I like you”. I would like to be more subtle about it.

Could anyone provide some tips or helpful advice?

Thank you for your help.