More interesting for the HN crowd I think is the article from the actual design company that did the redesign: https://www.pentagram.com/work/slack
Still, I love these kinds of process breakdowns. Having been involved in writing a few of my own, I know there’s probably a lot of pretentious nonsense to fill in the blanks (i.e. designers mess around a lot when working) but still it’s a nice read, short as it is.