Rather than undergo one enormous rescue mission, the team will try to make many minor alterations to the timeline to knock Iris’ death out of the timestream.
This will give each episode a specific purpose and a specific structure — not unlike Oliver Queen’s mission to right his father’s wrongs during the first season of Arrow.
Andrew Kreisberg recently spoke to EW about the latter half of The Flash’s third season and laid out that basic structure for how Barry Allen is going to try to save Iris.
As Team Flash begins to slowly but steadily learn new information about how the next six months will play out, they will manage to develop a “road map” comprised of particular tent pole moments that they will try to change.