qmk_firmware/layouts/default/planck_mit/info.json

{
    "keyboard_name": "Planck MIT (4x12) layout",
    "url": "",
    "maintainer": "qmk",
    "width": 12,
    "height": 4,
    "layouts": {
        "LAYOUT_planck_mit": {
            "layout": [
                {"x":0, "y":0},
                {"x":1, "y":0},
                {"x":2, "y":0},
                {"x":3, "y":0},
                {"x":4, "y":0},
                {"x":5, "y":0},
                {"x":6, "y":0},
                {"x":7, "y":0},
                {"x":8, "y":0},
                {"x":9, "y":0},
                {"x":10, "y":0},
                {"x":11, "y":0},

                {"x":0, "y":1},
                {"x":1, "y":1},
                {"x":2, "y":1},
                {"x":3, "y":1},
                {"x":4, "y":1},
                {"x":5, "y":1},
                {"x":6, "y":1},
                {"x":7, "y":1},
                {"x":8, "y":1},
                {"x":9, "y":1},
                {"x":10, "y":1},
                {"x":11, "y":1},

                {"x":0, "y":2},
                {"x":1, "y":2},
                {"x":2, "y":2},
                {"x":3, "y":2},
                {"x":4, "y":2},
                {"x":5, "y":2},
                {"x":6, "y":2},
                {"x":7, "y":2},
                {"x":8, "y":2},
                {"x":9, "y":2},
                {"x":10, "y":2},
                {"x":11, "y":2},

                {"x":0, "y":3},
                {"x":1, "y":3},
                {"x":2, "y":3},
                {"x":3, "y":3},
                {"x":4, "y":3},
                {"x":5, "y":3, "w":2},
                {"x":7, "y":3},
                {"x":8, "y":3},
                {"x":9, "y":3},
                {"x":10, "y":3},
                {"x":11, "y":3}
            ]
        }
    }
}