unnamedArena - FFXIV
The consistent rule for positions and flexing in this mechanic is to look at the visual conga line formed on the field.

All of the static spots going from L->R are T/H2 T/H1 DPS1 DPS2, which will be the shape of either group in the initial conga line on slide 1.

For flexing, it is always the players closer to the center of the two towers that need to flex. So for example, after Odd Towers, the two previous STACK players will be the ones that need to flex. Likewise, after Even Towers, the two previous CONE players will be the ones that prioritize flexing for doubled up stack.

This consistent rules makes it very obvious when you need to flex, without needing to check if your partner's name in the party list.

Static spots also greatly reduces mental burden, meaning remembering your icon from after tower 3 until tower 8 is much easier.