Yep! It’s the Aluminum Phosphate. I built pretty much all of the Meng Qi Paper Circuit PCBs, and I think that one was the most difficult and time consuming. I spent ages trying to figure out why I couldn’t get sound out of it… and it ended up being that I was using a 9V power supply with the wrong polarity >_<
Those huge holes on the bottom are a good spot for touchable banana jacks. I think I found a bunch either on eBay or AliExpress, but this was a few years back. Alternatively, Meng Qi has a video where he built one with a bunch of momentary arcade buttons for connecting the various points.