minecraft-assets/data/minecraft/recipe/blue_banner.json

{
  "type": "minecraft:crafting_shaped",
  "category": "misc",
  "group": "banner",
  "key": {
    "#": "minecraft:blue_wool",
    "|": "minecraft:stick"
  },
  "pattern": [
    "###",
    "###",
    " | "
  ],
  "result": {
    "count": 1,
    "id": "minecraft:blue_banner"
  }
}