qmk_firmware/keyboards/bigseries/3key/info.json

{
  "keyboard_name": "Big Series 3-Key",
  "url": "",
  "maintainer": "qmk",
  "width": 12,
  "height": 4,
  "layouts": {
    "LAYOUT": {
      "layout": [{"x":0, "y":0, "w":4, "h":4}, {"x":4, "y":0, "w":4, "h":4}, {"x":8, "y":0, "w":4, "h":4}]
    }
  }
}