app.layout.json

[{"name":"root","type": "core/template",
  "children": [
    {"name": "header","type": "core/template"},
    {"name": "body","type":"core/template",
      "children": [
        {"name": "body.left", "type": "core/template"},
        {"name": "body.right", "type": "core/template"},
        {"name": "body.main", "type": "core/template"}
      ]
    },
    {"name": "footer", "type":"core/template"}
  ]
}]

app.user.json

[
  {
    "reference": "body", 
    "actions":[
      {"setTemplate":"one-column"},
      {"removeChildren":["body.left","body.right"]}
    ]
  },
  {
    "refrence": "body.main",
    "children": [
      {"name":"user", "type": "user/listing"}
    ]
  }
]