This probably isn't a new idea, but here's a method I used to ensure by aquarium's bottom trim was making even, and perfect contact everywhere:
I applied epoxy where the tank would be sitting, and then covered it in plastic. I set the tank down on top of the plastic, so the soft epoxy would take its perfect shape, and let the epoxy set up.
I applied epoxy where the tank would be sitting, and then covered it in plastic. I set the tank down on top of the plastic, so the soft epoxy would take its perfect shape, and let the epoxy set up.