Just curious - did you check out Ursula's posts in the thread I linked to above? I had been hoping you would get a good visual from those posts.
I agree - for me, the pelvic tuck thing never worked. That is just not a position my body can comfortably maintain for more than a minute or two - not helpful for me for a long ski day.
What you're supposed to be doing with your torso is matching the angle of your back to the angle of your shin by flexing at the hip. (The angle from knee to hip also matches but in the other direction). I practiced it by looking in a mirror. Whether I was short (deeply flexed), medium or tall, those angles must still match. All 3 joints must be flexed or extended proportionally. And all the while, your weight should be centered over the balls of your feet - just like when you're shooting a free throw. You can see what I mean in Ursula's stick figures. That's it!
Not complicated, but it DOES take practice to get the feeling into your body.
Don't try to take this into steeper terrain until you have it nailed on easy green slopes.
That said - it falls apart in steeper terrain if you don't commit your body down the fall line enough. As the skis tilt down the slope, you must send your body down the fall line so that your body stays perpendicular to the skis. Otherwise you are instantly in the back seat.