The open source FPGA thread is here
https://bitcointalk.org/index.php?topic=9047.0 but its a bit quiet nowadays, probably because FPGAs are passing out of profitabiity (still OK for existing amortized kit, but certainly not for new kit). Hell, even ASICs are unprofitable these days, unless you managed to get an early preorder delivered in time.
Anyway the usual route is to buy a custom built mining board. People have used professional development boards, but they generally can't cope with the heat for high performance, so have to be throttled back. They also tend to be more expensive than the custom boards, so only make sense if you've already got one. You seem to want to build your own "from the ground up". That's pretty challenging (but goes nicely with your moniker). It has been done, to various degrees of success. For anything but the lowest spec FPGAs, you're looking at BGA packaging which is very advanced homebrew assembly, typically needing 4-layer PCB's with fine-pitched vias and reflow soldering gear (you might get away with 2-layers and the "skillet" approach, but its not recommended, lol). Have a seach through the site for FPGA, BGA, reflow, skillet (lol), especially the custom hardware thread.
BTW you won't recoup
any of your capital. By the time you get it working it will only be mining dust, probably not even covering its electricity cost to run it. But good luck, and power to all the tinkerers
