The neutral zone can be set by players from either team. A standard yellow flag is used to mark the current spot of the ball and the subsequent lines of scrimmage.
Technically the defense is responsible for spotting the ball. This becomes important in 'hurry up' play.
Not moving the flag to the new spot in a timely manner is a delay of game penalty (4 paces, and clock stops).
Last updated: Jan.31.2018