Li Shenron
Legend
Since opportunity attacks basically don't exist, and flanking is pointless, you can just say that all of the melee people run forward and all of the ranged people hang back.
Why do you say that OA don't exist? I think I've always used OA in TotM. Even without tracking positions or distances exactly, it's trivial to know who is in melee range. In fact, OA are part of the "mandatory" core rules of 5e which do not assume miniatures.
Flanking is presented as an option rule with miniatures only, but it's not difficult to use it also in TotM. You only need to say which 2 creatures are on opposite sides of a target. Whenever a creature has a turn, if it moves then the flanking conditions can change: a flanking creature and its flanking partner can lose their flanking position and/or a non-flanking creature as well as another who is also non-flanking the same target can become flanking. Still at any given time you have flanking in pairs (at least when everyone is medium size... rules are a bit foggy when they talk about "opposite sides" of a large target, or at least the visual example in the DMG can be misleading).