Rogue 3 (thief), monk 8 (open hand)
Pre-combat: use Wholeness of Body for an extra bonus action for 3 turns
Turn 1: action attack x2, flurry of blows 3x for 6 attacks.
If you have maxed strength and pick tavern brawler, each attack is +10 damage on top of the martial arts die. Easy 100 damage per turn with Manifestation of Soul and an ok wisdom score (ie + 1d4 + 3-5 per hit passively)
This feels like a pretty tame way to use unlimited freecast, honestly. By the time you have everything you need, there are only a few fights left that it’s worth using on, as well.