I would say your best bet is to not go too crazy on the stance without any gear. If you're going to start with box squats, start with a high box and work down. You want to gradually work down on the box height in order to make sure your form doesn't breakdown. I'm willing to bet that your posterior chain isn't used to being the primary mover while squatting. If you start with too low of a box, you wont sit back right and likely collapse to the box. It took me over a month of squat workout to get down to a respectable height if my memory serves me right.