I think putting "male name/male name" when listing pairings is all the slash warning anyone needs. Even if you have unisex names, people know who the characters are in their fandom. Even if multifandom communities, you have to list the fandom, and if you're reading for a fandom you don't know for whatever reason and are shocked to find that Sam and Chris are both women, then you should probably be doing a bit more research before reading a fic without knowing the source material. Especially since slash is more prevalent in some fandoms than others - who knows, Sam/Chris might be the big fandom OTP.