Deciding Set

[Zoochy]

When should the Timer start the 3 minutes before the deciding set? I have seen the clock start as the R2 is gathering the captains to do the Coin Toss. As well as after the Coin Toss has been performed and the information has been communicated to R1.
In sets before the deciding set, coaches knew if their team was Serving or Receiving. Thus they would better prepared to submit the lineup card. Now they would have to wait until the coin toss, which takes at least 45 seconds.
There are many schools that keep the same lineup for every set. But there are coaches that adjust players based upon Serve/Receive or how players are playing.
I know there are many questions, but the main question is when is the 3 minutes started?