Ignoring any player at/beyond midfield, we'll look at how the flat mark wall defense flows just from the handlers perspective.
While the stall count increases and the handlers decide it's best not to force a throw through the middle of our wall, they look to their handlers on the side.
So the offense then passes the disc to their handler on the side. Our wall then moves to pinch off the throw back to the middle handler and #4, the wing, looks to block all throws up the line.
Our wall pinches the throw back to the middle, which forces the ratchet (middle handler) to move backwards to get an open passing lane. Our #1, wing on the left, slides in to take away a throw from one side of the field to the other, which would end up being a break throw.
Offense and defense effectively reset. At least in a perfect world. Most often the offense was forced backwards. They were able to get passes through the middle and up the sidelines (we've ignored the other 7 players on the field for simplicity sake).