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

{
  "type": "minecraft:crafting_shaped",
  "category": "equipment",
  "key": {
    "X": "minecraft:leather"
  },
  "pattern": [
    "X X",
    "X X"
  ],
  "result": {
    "count": 1,
    "id": "minecraft:leather_boots"
  }
}