I am with Mike on this one, I have approached it from both shaped and square and have ended up doing a combination of them both. I do as much of the rifle as I can with the stock square including installing most butt plates. It is much easier to hold the stock in the square, locate and drill holes, inlet the barrel, drill the ramrod hole and inlet the triggers and the guard. I shape the stock close to finish surface to install the rear pipe and nose cap. When I say square I do not necessarily mean full blank thickness. I do trim the blank down as I go but I do keep flat surfaces as long as I can.
I also agree with the guys who say to remove as much wood as possible before inletting a part. There is no sense inletting down through wood that is going to be removed. Get rid of the excess before starting and your life will be much easier.