I don't know if it's still a thing but during many interviews I did for software dev. positions I was simply asked to perform a 30 minute coding task on paper and left alone in a room to do it, plus maybe another 10-20 minutes to fill a questionnaire related to the language of choice.

Thinking about it, I think this is a good approach. Duration is right, you're left alone to think, and it's pen and paper so while low tech it does show your own reasoning and your own knowledge of the language (a typo here or there is not critical to the exercise).