qmk_firmware/quantum/template/base/info.json

{
    "keyboard_name": "%KEYBOARD%",
    "url": "",
    "maintainer": "%YOUR_NAME%",
    "width": 3,
    "height": 2,
    "layouts": {
        "LAYOUT": {
            "layout": [
                {"label":"k00", "x":0, "y":0},
                {"label":"k01", "x":1, "y":0},
                {"label":"k02", "x":2, "y":0},
                {"label":"k10", "x":0, "y":1, "w":1.5},
                {"label":"k12", "x":1.5, "y":1, "w":1.5}
            ]
        }
    }
}