I usually put down a short pole in an open area then put a floor piece on top. That will fit four or five hives on it. The only thing you need to worry about is not having a wall too close the sides. Putting them on a roof also works if your base doesn't have much room inside its defenses. You can easily walk on a 26 degree roof.

I think they just wanted to make sure players weren't stashing them indoors.