when i was thinking about Phil’s grid jig design ( Grid Jig "Koi" ), another idea came into my head.
design principles:
- should be impossible for a beginner to mess up
- should be easy for beginners to make using standardized fabrication processes
the idea is for two pieces of right-angled metal, with holes drilled at the appropriate positions on one face, with the hole-y faces separated by 40mm (the size of a beam), and a flat piece at the bottom, which together creates a channel for the proto beam to go between.
like Phil’s notched strip jig, the jig is used to hold the wood in position under the drill , using an initial hole (on the side) connected to the jig with a bolt. the procedure is similar: put the bolt in, drill, take the bolt out, move the beam forward one hole, repeat. 
i do feel like this design could be made with sheet metal (something i’d like to learn how to do, as sheet metal fabrication is more available than CNC machine fabrication here in New Zealand) and standard bolts.
i started a GitHub repo to create 2d dxf files for the sheet metal fabrication and 3d stl files to see what the final product should look like: GitHub - villagekit/gridjig-fold