Now, the Frisky is officially a Slack office— similar to HBO , eBay, Mint, Venmo, Sony, Nordstroms, Crossfit, Dell, the New York Occasions, GoDaddy, PayPal, Blue Bottle Coffee, Urban Outfitters, BuzzFeed, Gawker, and Slate. It is late morning on a Thursday in September, and Slack Technologies CEO Stewart Butterfield has…