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

{
  "type": "minecraft:crafting_shaped",
  "category": "building",
  "key": {
    "#": [
      "minecraft:purpur_block",
      "minecraft:purpur_pillar"
    ]
  },
  "pattern": [
    "###"
  ],
  "result": {
    "count": 6,
    "id": "minecraft:purpur_slab"
  }
}