This is a simple type of self-working card trick that works on its own, as the name implies. As in the case of many other card tricks, you need to have a spectator so as to witness how the trick is played. If you are a performer, then let a spectator shuffle the cards to ensure all the cards in the deck are randomly placed. After that, choose any two cards from the top of the deck and place them inside the cards one by one wherever the spectator wants. As you bring them out with the other two cards adjacent to them, they will be the same cards with different suits.
After you have placed the cards in the deck as per the spectator’s wish, fan them on the table such that you are easily able to see the two cards that have been placed earlier inside the deck with their faces up.