Once your dog has used the pad on the machine for a few days, reduce its size by folding or cutting it in half. After a few more days fold or cut the pad in quarters. Eventually, remove the pad completely.
If your dog resists going on the platform once the pad size is reduced or the pad is removed, put a pad the same size as the last one successfully used on the platform. Then after a few days try gradually reducing the size of the pad again.