qmk_firmware/layouts/default/ortho_3x10/info.json

{
    "keyboard_name": "3x10 ortholinear layout",
    "url": "",
    "maintainer": "qmk",
    "width": 10,
    "height": 3,
    "layouts": {
        "LAYOUT_ortho_3x10": {
            "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":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":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}
            ]
        }
    }
}