SiegeMachines/src/main/resources/data/siegemachines/recipes/turret_base.json

{
  "type": "siegemachines:siege_workbench",
  "pattern": [
    "bp",
    "  "
  ],
  "key": {
    "b": {
      "item": "siegemachines:beam",
      "count": 2
    },
    "p": {
      "tag": "minecraft:planks",
      "count": 2
    }
  },
  "result": {
    "item": "siegemachines:turret_base",
    "count": 1
  }
}