src/main/resources/assets/aether_legacy/recipes/saddle.json

{
  "type": "minecraft:crafting_shaped",
  "pattern": [
    "LLL",
    "LSL"
  ],
  "key": {
    "S": {
      "item": "minecraft:string"
    },
    "L": {
      "item": "minecraft:leather"
    }
  },
  "result": {
    "item": "minecraft:saddle"
  }
}