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

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