Structure Generation

Hello, I'm trying to add a new structure to the world, but, this structure  is embedded in the surface and not on top of it, and I don't understand why t.t
structure/lucky_block.json
{
  "type": "minecraft:jigsaw",
  "biomes": "#lucky_blocks_world:has_lucky_block",
  "step": "surface_structures",
  "spawn_overrides": {},
  "terrain_adaptation": "beard_box",
  "start_pool": "lucky_blocks_world:lucky_block",
  "size": 1,
  "start_height": {
    "absolute": 0
  },
  "project_start_to_heightmap": "WORLD_SURFACE_WG",
  "liquid_settings": "ignore_waterlogging",
  "max_distance_from_center": 100,
  "use_expansion_hack": false
}

structure_set/lucky_block.json
{
  "structures": [
    {
      "structure": "lucky_blocks_world:lucky_block",
      "weight": 1
    }
  ],
  "placement": {
    "type": "minecraft:random_spread",
    "salt": 1256891,
    "spacing": 35,
    "separation": 25,
    "frequency": 0.75,
    "spread_type": "triangular",
    "frequency_reduction_method": "default"
  }
}

template_pool/lucky_block.json
{
  "name": "lucky_blocks_world:lucky_block",
  "fallback": "minecraft:empty",
  "elements": [
    {
      "weight": 150,
      "element": {
        "element_type": "minecraft:single_pool_element",
        "projection": "rigid",
        "location": "lucky_blocks_world:lucky_block",
        "processors": "minecraft:empty"
      }
    }
  ]
}