I don't think "last" can be translated literally in most situations, or at least shouldn't. "Last" will be very much understood from context in most cases. I'd come up with:
"When did we last meet?"
この前会ったのはいつ？ Kono mae atta no wa itsu?
"When did you last see her?"
彼女を見たのはいつだった？ Kanojo o mita no wa itsu datta?
"When did you last do the laundry?"
洗濯したのはいつだった？ Sentakushita no wa itsu datta?
いつ洗濯したんですか？ Itsu sentakushitan desu ka?
この前 is a common way to say "last time", but it's usually only used if you find yourself in exactly the same situation as before and want to refer to the last time this happened. You can't usually apply it if you're asking another person when he last did something if you had no part in that "last time".
Usually the best way is to simply phrase the question in past tense, which very much implies that you're asking for the last time something happened. If you want to very explicitly say "most recently", 一番最近 ichiban saikin should do.