Extremely slow and terrible process. Applied online, and was reached out to by possibly the most non-enthusiastic recruiter I have ever encountered. During our first brief chat, she failed to convey her passion for the product and depressed my morale for the role as well.
After the phone screen, I received a "coding challenge" which involved building a lightbox using JavaScript. Not only were the specs for this project lacking, there was a significant lack of feedback given from the recruiter based on early questions.
Slack needs to improve its recruiting pipeline and process, or it will recede into the shadows much like Yammer did, not matter what Mr Butterfield might say.