On receiving the selected card pretend to shuffle it amongst the others,
but really bring it to the top. The rest of the pack you arrange with
their edges even, whilst the top card projects a little.
On pushing that card a little out, at the same time as you drop the pack
perpendicularly, the resistance of the air will turn the single card
upside down, so that it will rest face up on the top of the fallen
cards.