You have ten seconds to look at and rearrange the cards in your library. At the end of those ten seconds, if you're touching one or more of those cards, shuffle your library.
You canâ€™t change the contents of the library.
Have another player keep time and announce when the ten seconds are up. If youâ€™re still touching any cards in your library when time is up, you have to shuffle your library, undoing your ordering.
At the end of the ten seconds, your library must again be a single face-down pile of cards. If itâ€™s not, you must shuffle your library, even if you werenâ€™t touching it when time expired.