Assembly requires a few M3 nuts and bolts (4 of each). Simply bolt the top shoulder to the base plate. If using PCBs thicker than 0.8mm, you can print a series of 0.2mm thick spacers (or whatever thickness you need) and insert them between the base plate and top shoulder. Install the corner and/or straight supports in the required position to support the PCBs while applying paste.

I use tracing paper/vellum cut with a desktop laser CNC, which works great with this jig.