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

{
  "type": "minecraft:crafting_shaped",
  "category": "redstone",
  "key": {
    "#": "minecraft:polished_blackstone"
  },
  "pattern": [
    "##"
  ],
  "result": {
    "count": 1,
    "id": "minecraft:polished_blackstone_pressure_plate"
  }
}