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

{
  "type": "minecraft:crafting_shaped",
  "category": "misc",
  "group": "gold_ingot",
  "key": {
    "#": "minecraft:gold_nugget"
  },
  "pattern": [
    "###",
    "###",
    "###"
  ],
  "result": {
    "count": 1,
    "id": "minecraft:gold_ingot"
  }
}