The buttons, their cover, and the compliant bits that act as a spring can be 3D printed as a complete unit that requires no assembly, and can be used fresh off the print bed. The design is still ...

How do you make a pogo pin jig? With a 3D printer, of course. The ISP header wasn’t populated to give the board a slim profile, but this means a jig of sorts would be needed to program the WIOT.