How did you ask someone to be your FWB?

I know it's usually just assumed, but there's this guy and we're both reallyyy sexually attracted to each other but neither of us has made the move yet...I want to ask him to be my FWB, I want him to know it's strictly sex and nothing more but idk how to do that? Do I just suck it up and shoot him a text that says "Hey wanna be fuck buddies?" How did ya"ll make it happen??? 😂😂😂