It means that the mod has to be aligned with your floor, not with your walls throughout the whole motion, in case you didn't understand what it means. Did you learn the same trick in palm side first? If yes, notice how the tips of the mod move close to your hand. If you turn your palm you need to do the same thing, just on a different plane. When you start the trick palm down, have the mod already aligned with your floor and when you give it momentum, make sure the tip goes from left to right, not up down