try it one way, and ski it, see how it feels. then try the other way and see how that skis. This is a great way if you have a good feel on the snow for what your skis are doing.
other option. set up a mirror in front of you, so you can stand in a ski stance, and look forward, but still see yout boots.
remove liners and place bootbeds in the shell only. center you foot on the footbed, and then center the footbed (and your foot) in the shell. helps to use some straight lines (hard wood floors?) to make sure that the boots are forward, and even, and the right stance width.
flex forward and back a few times, and you are looking for even spacing between your shin/calf and the ski boot shell, on both boots, on medial and lateral sides.
adjust the upper cuff so that the spaces are the same on both legs, both sides.