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

{
  "type": "minecraft:crafting_shapeless",
  "category": "equipment",
  "ingredients": [
    "minecraft:iron_ingot",
    "minecraft:flint"
  ],
  "result": {
    "count": 1,
    "id": "minecraft:flint_and_steel"
  }
}