Structure Generation

am I able to make structures spawn on actual terrain rather than having them generate in the air with islands? I've tried:
{
  "type": "minecraft:jigsaw",
  "biomes": "azure:summer_islands",
  "step": "surface_structures",
  "spawn_overrides": {},
  "terrain_adaptation": "none",
  "start_pool": "azure:apple",
  "size": 1,
  "start_height": {
    "relative_to_heightmap": 0
  },
  "project_start_to_heightmap": "WORLD_SURFACE_WG",
  "max_distance_from_center": 1,
  "use_expansion_hack": false
}

and messed a bunch with the start height - trying 'absolute' values