Here's all the pics I have of mine... Cost me about 50 bucks for the zip ties, 20 feet of zero gauge, and the little terminal male/female connections. It isn't track legal or whatever, but I don't give a ****, cause I don't track my car!
Just use nylon webbing strap. if you don't want the box all you need to do is make a simple tray and run a strap around the whole thing (works best with the straps that don't have ratchets just the spring loaded stopper).