His region would have to 1st, nominate him for the honor of coaching in the game, next coach himself would have to express interest in being the HC of the South, All 5 HC from each region have an opportunity to throw their hat in the ring to be HC of the North or South. From there, if there are muliptle hats in the ring, IFCA members from each region's such as Region Director, Ast Coach Rep, etc etc get a an email with the resume of each coach who applied.
Only time that I know of it wasn't done this way was 50th, when the Legends were brought back