Since the game’s 0.9.0.0 update (The Caves & Ladders Update), flat world generation has been finicky. After testing over 200 seeds, here are the only five that generate true flat terrain (Y-level 70) with full ore distribution and zero water spawns.
What if your world was flat, but a game update turned it into a mess? You have a thriving colony hanging in mid-air above a chasm. You need the . colony survival flat world seed fix
Audit seed derivation and propagation