src/main/resources/assets/aether_legacy/recipes/iron_pendant.json

{
  "type": "minecraft:crafting_shaped",
  "pattern": [
    "SSS",
    "S S",
    " I "
  ],
  "key": {
    "I": {
      "item": "minecraft:iron_ingot"
    },
    "S": {
      "item": "minecraft:string"
    }
  },
  "result": {
    "item": "aether_legacy:iron_pendant"
  }
}