Blah blah read the description.
Step one was getting all the bits together I wanted, then working out all the bits I needed. So Orange Pi, router, step down and usb-sata. Then to work out what I needed to get these all nice and together.
To power the router, and break out the USB ports on the Oppai, I decided on these little USB OTG adaptors
They're designed to go into a male plug of a USB device, essentially turning it into an OTG device you can plug into a phone, but paired with female microUSB breakouts I found it to be much more useful.
A male to female ethernet cable would allow me to pass through the routers connections to the front of the housing, so throw one of those on the shopping list.
A DIY male SATA power connector also helps out. Other things I added where a pretty button, some male and female RCA connectors for power, a fan or two, and various other bits and bobs.
Depending on your needs, if you end up making something similar you'll probably have a completely different list of parts. This was just mine.
Anyway, nearly ready to go!