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

{
  "type": "minecraft:crafting_shaped",
  "category": "building",
  "group": "bark",
  "key": {
    "#": "minecraft:birch_log"
  },
  "pattern": [
    "##",
    "##"
  ],
  "result": {
    "count": 3,
    "id": "minecraft:birch_wood"
  }
}