Winner winner chicken dinner! That's the only way that I've ever managed to do it with perfect accuracy. Hang the drawer box and apply the drawer fronts with a brad or two with the drawer closed. Using some shims as spacers helps get the reveal right. Then I fasten them from the back side with a couple screws once they're positioned.You can also make and mount the drawer then attach a drawer face to the existing drawer and center the face in the opening. Only thing to remember is to allow for the thickness of the drawer face when building and mounting the drawers.