Page 75 - Turkey Book from Meathead

If you want to keep the wishbone intact because you know it can bring you a winning lottery ticket, first place the chicken breast-side up with the neck cavity facing you. Work your fingers under the skin at the neck and locate the position of the wishbone with your fingers. With a paring knife, make two shallow cuts in the breast just above each of the longer bones of the wishbone. Push your fingers firmly through the cuts and work them around the long bones to loosen each side, then make a small horizontal cut directly above the very top of the wishbone to free it. Work your fingers all the way around the whole wishbone and pull it out of the meat. You can dry it and snap it with your favorite kitchen helper to see who gets the good luck.
You now have a spatchcocked bird. Here's a short video of the entire process.