minecraft-assets/assets/minecraft/recipes/gray_banner.json

{
  "type": "crafting_shaped",
  "pattern": [
    "###",
    "###",
    " | "
  ],
  "key": {
    "#": {
      "item": "minecraft:wool",
      "data": 7
    },
    "|": {
      "item": "minecraft:stick"
    }
  },
  "result": {
    "item": "minecraft:banner",
    "data": 8
  }
}