To be honest, this build is pretty advanced and I wouldn’t recommend as a first synth DIY project.

In short I assume anyone who wants to build this synth generally understands the concept of subtractive synthesis, basic electronics, can read schematics and PCBs (using KiCad) and has experience in soldering. I’ve written a build guide which has a “prerequisites” section as well as details on how to order PCBs and assembly steps: https://www.shmoergh.com/hog-build-guide/

The schematics might also be a good resource to dig deeer and understand the building blocks of an analog synth.