How do I go about reaching out to my boss to sleep with him after resigning?

We’re only a couple years apart in age (mid twenties) and worked together quite a while. I’m attracted to him but never actually acted on it myself. He used to flirt with me in the past (extra attention out of nowhere, subtly checking me out, talking up his job and money, playful/sneaky looks and smirks.) but I kind of shut it down and told him he was being too friendly when he asked. He got the hint and backed off. He blew hot and cold with me for weeks after before things eventually went back to work mode. Months pass and he’s randomly being chatty with me again, standing just a bit closer than usual and points a hair out on my hat for me. I say “oh where?” And he brushes it away while in front of other higher ups. He immediately says “just looking out for you.” Then proceeds to talk to me about the subject of my hat. I catch him looking in my direction after that. Would I have to be the one to reach out here first?