I've been looking for a guide to making a wiring harness from scratch and I can't seem to find one. Anyone got any leads?
There aren't really any guides as such, all you really need is a diagram.

A good way to do it is to get a piece of cardboard and mark where the controls on the guitar are, and then put holes in the cardboard and mount the pots and switch to the cardboard, so you can wire them outside of the guitar (which can be a lot easier than trying to do it in the control cavity)