A poker player's picnic

Start by doing a controlled shuffle keeping the four aces on top.

Then, ask the spectator to cut the deck in half, and these two parts in half again. Keep track of the pile originally on top.

Now, give 2 piles to the spectator and 2 to you, but make sure you have the pile with the aces ! Shuffle each pile, while keeping again the aces on top.

Start with the pile at the other side of the one with the aces. Swap 3 cards from top to bottom, then place one card on top of each other pile. Do this with each pile ending with the aces.

Flip the card on top of each pile, these will be the four aces.