Someone was asking for how to do this today, and I think this tutorial does a rather wonderful job of explaining the process. Enjoy!
The True Adventures of a High School Librarian: Flipping Your Class Easily with Google Hangouts On Air
I absolutely love using Google+ Hangouts On Air to record PD sessions and for recording Flipped Classroom lessons. It is quick, simple, and seamless once you have gone through an initial, one time, slightly convoluted and aggravating set up process.