Agree with below, no boxers. No towel either. Although, a towel hasn't stopped most ladies for me. 95% of places offer something, so just a few basics. Personally, I don't touch ladies without permission, I don't start face up, I have never talked about what I want during the back massage, I don't leave tip out first and I almost never have anything "up". Yet, I've been offered L1 almost every time I go somewhere. So the boxers were probably your biggest obstacle. The things people suggest below will only make it that much easier for you. Especially if you want more than L1.

If the ladies are in jeans or spandex and TShirts, anything is possible but ive found L1 is most likely. If they come to the room in lingere or any kind of outfit that has nothing to do with massage, above L1 is more likely.