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

{
  "type": "minecraft:crafting_shaped",
  "pattern": [
    "###"
  ],
  "key": {
    "#": [
      {
        "item": "minecraft:sandstone"
      },
      {
        "item": "minecraft:chiseled_sandstone"
      }
    ]
  },
  "result": {
    "item": "minecraft:sandstone_slab",
    "count": 6
  }
}