How do i be friends with my ex ??

Ok i asked the FWB question and ye fair points. But i know for absolute sure that i can't not have him in my life because even if he isnt a bf I consider him my Best Friend and want him as part of my life DEFINITLY. But how do i do it? I mean im still physically attracted to him even though i don't want him as a bf due to my own cirstances. Yes i still love him. But is it weird to sleep at his house even if we don't have ? Is it weird to still flirt with him? Is it weird to still feel compelled to want to help him out and be around him?