Custom dimension/flat generator settings

- layers: (Required, but can be empty) Layer settings. This list is interpreted from top to bottom, starting at world bottom.
  - : A superflat layer.
    - height: The height of this layer. Value between 0 and 4064 (both inclusive) .
    - block: (optional, defaults to minecraft:air) The block ID.
- biome: (optional, defaults to plains) The ID of the single biome of the world.
- lakes: (optional, defaults to false) Whether or not to generate lava lakes. If set to true, then lava lakes (lake_lava_underground and lake_lava_surface) generate often even in biomes where lakes don't normally generate.
- features: (optional, defaults to false) Whether or not to generate biome-specific placed features. Note that the placed features in the step UNDERGROUND_STRUCTURES and SURFACE_STRUCTURES never generates. If the biome is not minecraft:void, but layers is empty or has only air, no placed feature generates.
- structure_overrides: (optional, defaults to all the structure sets) List of structure sets to use. Can be a ID of structure set or a structure set tag, or a list of structure set IDs.