Hey guys needed some help for sub box

I want to buy a new sub and build the box, but idk how to do it or how to measure everything for the best sound output. The sub I’m currently looking to buy is [this one](https://shop.singhelectronics.ca/skar-audio-evl-12-12-1250-watts-rms-car-subwoofer/), and I already have [this AMP](https://shop.singhelectronics.ca/skar-audio-rp-1200-1d-1200w-rms-class-d-monoblock-car-amplifier/) (if you have better subs to recommend with this amp please feel free to tell me).

Also while I’m here do you guys know how to spot a good ground to wire the amp? I’m already grounded on some random bolt I found connecting to the body of my car, but I’m pretty sure it could be better. Thanks for the help!