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

{
  "type": "minecraft:crafting_shapeless",
  "category": "equipment",
  "ingredients": [
    {
      "item": "minecraft:iron_ingot"
    },
    {
      "item": "minecraft:flint"
    }
  ],
  "result": {
    "item": "minecraft:flint_and_steel"
  }
}