It's not to difficult and seeing as it's part of a flourish I see no reason why we can't "expose" it here (however, if a moderator feels differently, feel free to edit/delete thi post).
1. Hold the pack with your dominant hand in dealing position (index finger resting on the short edge furthest from your body).
2. With your free hand grasp the pack from above with your thumb in the centre of the short edge closest to your body, your index finger resting on the centre of the top card and your second and ring fingers resting on the furthest short edge.
3. Tilt your non-dominant hand back, lifting a third of the deck away from the rest, but leaving the short edge held by the thumb in contact with the remainder of the deck.
4. Hold this position as your non-dominant thumb, lifts up the second third of the deck away from the bottom stock of the deck. The second third should remain incontact with the bottom stock at the furthest short edge, held in place by the dominant index finger.
I hope that's clear, if not let me know and I'll try and redescribe it.
