I applied via the website. There were two phone screens: the first with a recruiter, followed by a second with the hiring manager. After that, I was asked to make a portfolio of relevant marketing projects for review. After that, I was given a take home assignment that took me 10-12 hours to complete. This was followed by an in-person panel presentation with several people at Slack's office in SF, followed by several individual interviews. It was a very thorough process. I thought I did well but a week later, I received a form rejection email from the recruiter. I wrote back hoping for some explanation but received no response. This was disappointing given the amount of work I'd put into the hiring process.