After putting glue on the walls and the rails on the bottom I put thin rubber on them to insulate the batteries from the steel and to add some small amount of  thermal insulation.

Once I got all of the batteries in I had to make sure that they were set up from the big battery box to the small and then I had to think about the wiring and when I was happy I put the rods in to clamp the them in place after that to put on the connectors.