overlay-variant-panther-goofy/scripts/disk_layout.json

{
  "metadata":{
    "rootdev_base": "/sys/devices/pci0000:00/0000:00:1f.2/ata1/host*/target*/*/block/sd*"
  },
  "parent": "legacy_disk_layout.json",
  "layouts":{
    "usb": [
      {
        "num": 3,
        "size":"2048 MiB",
        "fs_size":"2000 MiB"
      }
    ]
  }
}