minecraft-assets/assets/minecraft/blockstates/frosted_ice.json

{
  "variants": {
    "age=0": {
      "model": "minecraft:block/frosted_ice_0"
    },
    "age=1": {
      "model": "minecraft:block/frosted_ice_1"
    },
    "age=2": {
      "model": "minecraft:block/frosted_ice_2"
    },
    "age=3": {
      "model": "minecraft:block/frosted_ice_3"
    }
  }
}