The most important part of this stance, is the fact that the vast majority of your weight is supported by your back leg, and as such, it is developing leg strength. The front leg is purely there as an aid to balance. When teaching this technique, many senseis will sweep the front leg to ensure that it is barely supporting weight. If the student loses balance when the front leg is swept, then was too much weight on it. You should be able to lift the front foot from the ground with no additional change in posture or balance.
The back foot faces outwards at an angle of 45 degrees, whilst the front foot faces forwards. The front foot is positioned about one-and-a-half of your foot-lengths forward of the back foot. The unusual feature of this stance is the fact that the heel of the front foot is raised from the ground, placing what tiny amount of weight exists, on the ball of the foot. This provides tension in both the quadraceps (the front of the thigh) and calf muscles of the lead leg, enabling you to initiate a kick more quickly.
This stance can be used with the hips facing forwards or at an angle of 45 degrees. You can also turn your shoulders so that you are facing at a right angle to the direction of your stance, looking across your rear leg.
Ohgami suggests that the version with a 45 degree hip offset, is best-used for situations when your body rotation and block movement are in opposite directions. For example, when performing an Inside Shuto with your right hand, whilst turning your body anti-clockwise.
Don't make the stance too short
Don't stick your butt out
Don't lean forwards
Lift your front heel up high
Tuck your back knee in behind your front one - it shouldn't stick out at 45 degrees
Don't stand up tall