Create/src/generated/resources/assets/create/blockstates/fluid_tank.json

{
  "multipart": [
    {
      "when": {
        "top": "true"
      },
      "apply": {
        "model": "create:block/fluid_tank/block_top"
      }
    },
    {
      "apply": {
        "model": "create:block/fluid_tank/block_windows"
      }
    },
    {
      "when": {
        "bottom": "true"
      },
      "apply": {
        "model": "create:block/fluid_tank/block_bottom"
      }
    }
  ]
}