I straddle everything outside of the circle up to about 50-60 feet and I always line both feet up along the perpendicular line facing the basket. Make a + in the dirt from your mark on the ground and don't move your non disc any closer to the basket. Just make sure your disc foot is on the ground when you release.
Many people mistakenly believe your non disc foot needs to be farther away from the basket than your disc foot, but the rule is that it can not be any closer than your disc foot. If your feet are square along that perpendicular line than you are legal, just don't inch it closer. If anyone questions your legallity show them the perpendicular line and ask if they have a protractor or Tsquare in the bag.