minecraft-assets/data/minecraft/recipes/loom.json

{
  "type": "minecraft:crafting_shaped",
  "key": {
    "#": {
      "tag": "minecraft:planks"
    },
    "@": {
      "item": "minecraft:string"
    }
  },
  "pattern": [
    "@@",
    "##"
  ],
  "result": {
    "item": "minecraft:loom"
  }
}