I've built a couple of them. This helped.
https://drive.google.com/file/d/1dnn7DX4iclaRhZ4AuSF5vr2ujtyX_ywS/view
FWIW, I did not find the matrix switches 1-4 intuitive or particularly useful, but do enjoy everything else and the unique overdrive/dirt tones that can be harnessed.