How did Dobby iron his hands when he shouldn't have been allowed near clothes?

During Chamber of Secrets, Dobby is forced to iron his hands as a punishment for betraying the Malfoys' secrets to Harry. How did he do that? Wouldn't he have been able to free himself if he was 给 tasks which involved clothes?

Also, who (in story - in reality it was obviously JKR) would have come up with the house-elf clothes rule in the first place? I'd have thought that laundry would be one of the main tasks you'd want a house-elf helping with! Even though magic would make washing easier than it would be without, I'd imagine there'd still be some prestige in not having to do it yourself.