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

{
  "type": "minecraft:crafting_shaped",
  "group": "boat",
  "pattern": [
    "# #",
    "###"
  ],
  "key": {
    "#": {
      "item": "minecraft:birch_planks"
    }
  },
  "result": {
    "item": "minecraft:birch_boat"
  }
}