Very carefully... I actually had a stereo shop do it... they had a template which comes off the back wall in a triangular fashion. The speakers are basically touching the back of the seats. If I had it all over to do again, I would do something different. The box is really nowhere big enough for 12's. Not enough airspace to utilize their potential. 8's might be a better choice, or some type of tube (bazooka).

Ken

1984 Toyota 4x4 Truck, 4.88's, 32x11.50's, weber 32/36, aux gas tank, Warn 9500i, SR5 guages, tilt/altimeter, Alpine stereo with dual 12's behind the seats.