You hand the deck to a spectator and instruct him or her to shuffle the deck and select any card. You instruct them to lose the card into the deck without you touching it in anyway. No funny movements and you are completely clean at this point. The deck is now in their control the entire time. You then instruct the spectator to spell out the selected playing card, with each card dealt representing a letter. Once she does so, the audience will realize that the final letter will be the freely selected card.
THIS IS SPELL.