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

{
  "type": "minecraft:crafting_shaped",
  "pattern": [
    " S ",
    "SCS",
    "LLL"
  ],
  "key": {
    "L": {
      "tag": "minecraft:logs"
    },
    "S": {
      "item": "minecraft:stick"
    },
    "C": {
      "tag": "minecraft:coals"
    }
  },
  "result": {
    "item": "minecraft:campfire"
  }
}