I've had luck just removing the front screws and collapsing the box, and sliding it in from the front. Once it's in place, it's just a matter of reinstalling the screws.
I do recommend if you are going to use a factory crossover box mounted in the traditional location (the side of the glove box) you mount it to the box before you install the box. Trying to mount it after the box is installed is a real pain!