You turn toward the window behind you and you show there is nothing on.
Now you throw the deck on the window: all the cards snap the window and fall on the flour but one remains stuck to.
Even better: not only the card remains struck to the window but it’s on the other side. To prove it, you pass the hand on the window as if you wanted to catch it.
For an amazing ending, you take a cloth to wipe the window and the card vanishes… the audience is completely enjoyed.