renewable-resources/data/renewable/recipe/saddle.json

{
  "type": "minecraft:crafting_shaped",
  "category": "misc",
  "pattern": [
    "LLL",
    "LIL",
    "I I"
  ],
  "key": {
    "L": {
      "item": "minecraft:leather"
    },
    "I": {
      "item": "minecraft:iron_ingot"
    }
  },
  "result": {
    "id": "minecraft:saddle",
    "count": 1
  }
}