Hi Josh thanks for posting in the Community! The quickest way to unshare the document in Slack would be to navigate to the document in Lucidchart open the share dialog select the Slack toggle and then remove the channels listed that it is shared in. This won't remove the post in Slack but it will deactivate the share links so users in Slack can no longer accept the invitation and access the doc. If you'd like to fully remove the post from Slack as well I'd recommend reaching out to your company's Slack administrator. They should have the ability to remove the post. Hope this helps!