I found Casebook through a recruiter who they work with, which I think fast-tracked the interview process. The recruiter did some initial vetting on me in general before putting me up for jobs.
I had an initial interview with the CPO over google hangouts, then an in-office interview with the lead designer and a product manager. I was asked to prepare an example design exercise for this in-person interview, and reviewing it was the main content of the interview.