src/main/resources/assets/aether_legacy/recipes/skyroot_stairs.json

{
  "type": "minecraft:crafting_shaped",
  "pattern": [
    "#  ",
    "## ",
    "###"
  ],
  "key": {
    "#": {
      "item": "aether_legacy:skyroot_plank"
    }
  },
  "result": {
    "item": "aether_legacy:skyroot_stairs",
    "count": 4
  }
}