Not even any soldering involved. The ESP32 board they used just comes with everything needed, all attached with a couple socket connectors and optionally a ribbon cable for the camera:

https://www.seeedstudio.com/XIAO-ESP32S3-Sense-p-5639.html

It's pretty much the least sophisticated recording device possible. A kid could assemble it and prompt an LLM for the software like they did.