To build this jig you will need:
- the 3d printed parts here
- 4 pogo pins, like these P111-E 1.3mm Diameter, 33.30mm long test pins
- two Adafruit Perma-Proto Quarter boards
- some 4-40 0.75" or M3 20cm stand-offs
- a compatible JTAG/SWD, like this $8 STLink v2 one
Also handy is a small USB hub with per-port power switches, like this 4-port Sabrent USB hub
When soldering the pogo pins, make sure they poke out about 1.5mm from the 3d-printed base.