Feel free to check out the Awesome Bigley Baseball Association, a random historical debut league with 16 teams. We've been at it since 1961, and are currently in August of 1983. The St. Louis Browns are available, an organization that was recently one of four new expansion teams. It's a good group of experienced GMs. We SIM 7 days per evening, 7 days a week. Hit me up if you might be interested.
Oh, and we don't use Slack. Sorry. Just old fashioned e-mails.
http://abbacadaver.com/
Thanks!