Guardguy

I have a buddy who is going to make me a steel or aluminum security box for my JK. It will fit behind the rear seat like some of the Tuffy boxes do but it will have 6 sides for maximum security and make it easy for removal. The door will lock with a padlock and open towards the rear. The lock will not be accessible when the rear Jeep door is locked so you end up with double protection. My issue is how do I securely bolt this box down in the Jeep? It needs to be able to slide out the back when I want to remove it so I couldn't have bolts sticking inside the Jeep.