Slack interview questions

"Why Slack?", "Why this role?" Less "how would you deal with x problem in y situation" and more about your work style, background, and interest in the role/company. From my optic (after going through the gazillion rounds of interview with Google and FB) Slack's interview process was a breath of fresh air. Personally, I felt the people with whom I interviewed were empathetic, real, and incredibly nice (coincidentally these seem to be the values of the company), which ultimately set it apart from the others. I picked Slack because I think it really does place an emphasis on people and company culture.

What was your biggest mistake in x role 4 years ago?