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

{
  "type": "minecraft:crafting_shapeless",
  "group": "chest_boat",
  "ingredients": [
    {
      "item": "minecraft:chest"
    },
    {
      "item": "minecraft:dark_oak_boat"
    }
  ],
  "result": {
    "item": "minecraft:dark_oak_chest_boat"
  }
}