From Slack: You're reading this because you're looking for info on legacy custom integrations - an outdated way for teams to integrate with Slack. These integrations lack newer features and they will be deprecated and possibly removed in the future. We do not recommend their use.
Slack Channel Alerts
The Slack integration allows Alerts to be delivered to Slack channels.
Note: For Slack delivery to work, you need to configure a Slack Integration custom integration in Slack.
With Slack, you can
Communicate incident alerts to Slack channels
Share alert information with single users or other team channels
