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

{
    "keyboard_name": "Big Series 3-Key",
    "url": "",
    "maintainer": "qmk",
    "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}
            ]
        }
    }
}