The Clay Cliff are to find on the way to Lake Tekapo. You have to leave the main road in Omarama. After 14 km you will find a sign. The road passes private land. You have to pay 5 $ back in town :( .
You continue the track to a gate. You can pass this gate also with 2 wheel driven cars for another 500 m. Then the path gets very bad. Here you stop and after a few minutes walk you reach the Clay Cliffs.