If you have eight channels, I'd find someone breaking up a console and buy the relevant bits from an 8-channel bucket. I think the motherboard the channels plug into is in 8-channel sections. And you may find someone who will sell the metalwork for a single bucket. That would save you a lot of hard work
After that you'll need the PSUs and some logic to put the channels into the modes you want, faders if you want them, etc, etc, etc
This is pretty much the exact opposite of what Kags is suggesting so consider which way you want to go!