You can use a pencil and square to mark the ends of the square portion of the pommel. Then use a small handsaw (gents/dovetail) and cut into your layout lines. You do not need to cut in very far along the flats of the billet, maybe only a 1/16", a little deeper at the corners, maybe 1/4" depending on the size of the billet. When you start to turn this cut will prevent the corners from chipping out. You can use this technique for either a square bottomed or round bottomed pommel. Hope this helps.