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

{
  "type": "minecraft:crafting_shaped",
  "pattern": [
    "S",
    "P"
  ],
  "key": {
    "P": {
      "item": "minecraft:piston"
    },
    "S": {
      "item": "minecraft:slime_ball"
    }
  },
  "result": {
    "item": "minecraft:sticky_piston"
  }
}