Phonecall followed by take-home task.
I was told that the take-home task should take no more than 2-3 hours to complete. However, they were asking for a full end-to-end system to be built, tested and deployed to a production standard.
Take-home tasks should be an assessment of a canditates technical ability, not a measure of how long they can afford to spend on a task over the course of a week.