Phone screens with two separate recruiters then phone interviews with two separate hiring managers. Was flown out to San Francisco three weeks later for an on-site interview which involved a role play sales presentation given to two hiring managers, followed by three separate interviews with other managers. Overall I interviewed with seven different people, so they were very thorough. Entire process took over a month, and I was informed a week later that I did not get the job.
By the time I interviewed I did not especially want the position, and interestingly my acupuncturist told me during a session before the interview that he'd just replaced them with Amazon, and that his colleagues were doing so. This is something that I've seen and heard of more and more in my city. The people there seemed cool, though the manager whom I was to work for was cold, impersonal, made no effort to build rapport and seemed like a very corporate number-cruncher more interested in picking holes in my credentials, and I didn't think I would have liked working for him and probably showed it. Square is definitely not a start-up, and seems like it's going a very corporate route.