Flag Down Slow Whistle Situations
When there is a FDSW, the offended team, if they maintain possession on the foul outside the box will continue to play, just like they always have. If possession is lost outside the box, there will be an immediate whistle.
The difference is once the ball is in the attack box, there should be no stoppage of play unless the ball leaves the box, the D gains possession, the ball goes out of bounds, a goal is scored or the offended team commits a foul. This will take some getting used to by the officials, since we're so much in the habit of whistling as soon as the ball hits the ground. (I can vouch for that fact personally!)
The other big change is that any technical foul committed by the offending team during the FDSW (with possession OR even with a loose ball) will automatically become time-serving. This is a change from the normal call on a loose ball technical. As others have noted, this is a big advantage now for the attack. The thinking behind this is that the defense, if there was a loose ball during the continuing slow whistle, would have been encouraged to simply push an attack player from the back to draw a whistle without any penalty for doing so. Now there is a significant price to pay for that violation.
There was also a clarification that was posted earlier in the week;
With no flag down, if the ball is loose in the attack box and there is a personal foul on either team, there should be an immediate whistle. If the ball is loose and there is a technical foul by either team, it is the standard play-on procedure. All of this changes of course if there IS a flag down. Penalties by the offense would kill the slow whistle, penalties by the defense become time-serving, even loose-ball technicals.
One team was contending that the play should continue on if the attacking team has possession outside the box and the foul causes the ball to come loose. This is NOT the case, as stated clearly in the rules:
Slow-Whistle Technique
SECTION 8. If a defending player commits a foul against an attacking player and an attacking player has possession of the ball, and if the act of fouling does not cause the player in possession of the ball to lose possession, the official must drop a signal flag, make the verbal signal “flag down” and withhold his whistle... All of this also changes if the foul occurs in the box. If the fouled player drops the ball, play will continue!