Custom Slack Identity Provider: Bread & Butter

Log in to the Slack Developer site using your Slack account:

Enter your App Name. For App Name, we recommend using your organization or company name.
Choose your organization’s Workspace.
Click Create App.

In the left menu, go to Manage Distribution.
Under Share Your App with Other Workspaces expand Remove Hard Coded Information.
Check I’ve reviewed and removed any hard-coded information.
Click the Activate Public Distribution button.

In the left menu, go to Basic Information.
Under App Credentials, copy and save the Client ID and Client Secret for the Bread & Butter setup below.

Go to https://app.breadbutter.io/sign-in/
Click Sign In and authenticate (or Sign Up make a new account and authenticate).
Go to Settings in the left menu.
Click on Slack under SSO Settings > Social Accounts.
Select "Set Slack for Production".
Enter a custom name and description.
Enter the Client ID from the Slack setup steps above.
Enter the Client Secret from the Slack setup steps above.
Click Save.
Click the checkbox next to your new Slack provider to enable it.