To authorize the Slack application for issue reminders, first enable reminders in Slack channels by checking the "Allow reminders in Slack channels" box. Then, click "Configure Slack Access." This will open a new page where you'll select the desired Slack workspace and click "Allow" to grant the necessary permissions.
After granting permission, you'll see a "Everything is ok. Return to Jira" message. Clicking this will complete the Slack application authorization and redirect you to the "Reminders App Configuration" page.
To deauthorize the Slack application, simply click the "De-Authorize Slack Integration" button.