You remove the 4 aces from the deck, then with the deck face down you start to dribble the cards, inserting the aces face up one by one at various points.
You then spread the cards face up on the table where you can clearly see where the 4 aces are. (As they are the ONLY 4 cards facing the opposite way)
Then with just a magical gesture the 4 aces appear elsewhere!
