Self-Soldering Circuits [video]
It's a great hack and a cool demo that may have (very) limited real-life niche applications, but it's not really worth it unless you only make a couple of PCB per year and can't afford a small oven.Where this is great is that you can finely control the temperature of the board since you're in control of the current you pump into it.Where it's not great is that it uses a full layer and could cause issues if any of your PCB needs special considerations, when using high frequency clocks or RF (say implementing a switch mode power supply can be quite sensitive to how your layers are composed).  You also end-up with either a floating layer or a ground layer that has a long path instead of a real ground plane. That could also create noise issues.If you assemble a few PCB a year, a PCB oven is fairly cheap. You can make one with a regular US$50 oven and a PID control kit or just buy a dedicated one like the T-962 (that can be further hacked and improved) for about US$250 from Aliexpress.But that hack is still cool and Carl Bugeja's channel[1] has lots of fun projects that push PCB to new limits for hobbyists, showing what you can achieve with flex PCB in particular and using them as mechanical interfaces for creating motors, actuators, etc. It's a great channel![1]: https://www.youtube.com/@CarlBugeja