I won a dots and box bot competition years ago with this:
https://github.com/farnasirim/dots-and-lines-box. You can try it out in the terminal as easy as `g++ decision.cpp && ./a.out` and try the technique in the video in a 4x4 instance of the game against the bot. It plays fine in general, but I had not heard about the trick for the 4x4 case (outlined in the video) back then, so it doesn't support it.