Make sure you added an item before reading this tutorial, we will be using it.

So far, our item is obtainable through the creative menu or commands. To make it available to survival players, we'll add a crafting recipe for the item.

Create a file named custom_item.json under resources/data/tutorial/recipes/ (replace tutorial with your mod id if appropriate).
Recipe files are conventionally named after their output, but they can have any name. Here's an example recipe for the custom_item we made:

resources/data/tutorial/recipes/custom_item.json

{
  "type": "minecraft:crafting_shaped",
  "pattern": [
    "WWW",
    "WR ",
    "WWW"
  ],
  "key": {
    "W": {
      "tag": "minecraft:logs"
    },
    "R": {
      "item": "minecraft:redstone"
    }
  },
  "result": {
    "item": "tutorial:custom_item",
    "count": 4
  }
}

Breakdown of the recipe:

• type: This is a shaped crafting recipe.
• result: This is a crafting recipe for 4 tutorial:custom_item. The count field is optional. If you don't specify a count, it will default to 1.
• pattern: A pattern that represents the crafting recipe. Each letter represents one item. An empty space means that no item is required in that slot. What each letter represents is defined in key.
• key: What each letter in the pattern represents. W represents any item with the minecraft:logs tag (all logs). R represent the redstone item specificly. For more information about tags see here.
• category: The category of the item to display in the recipe book.

In total, the crafting recipe would look like this:

For more information about the format of basic recipes, see here.

Recipes can also be generated dynamically on runtime, for more information see here.

The type value can be changed so it can be used in the corresponding crafting block (stone cutter, blast furnace, smiting table, …), see all types and values here.

You can even create your own recipe type: Introduction to RecipeTypes