You can set up automation rules to send messages to private Slack channels using the Send Slack message action. To do this:
In Slack, go to incoming webhooks. You can also click the link to configure an incoming webhook in the Send slack message action.
Choose a channel to post messages to (or create a new one) and add an incoming webhook. You can change the selected channel at any time from within slack or from the Send Slack message action.
Copy the webhook URL from the integration settings in Slack.
Paste the webhook URL in the Send Slack message action.
Messages are sent to the default channel specified in your webhook, but you can override this by specifying another channel using the
#channelname, or send to a specific user using
@slackmemberID. Member IDs can be found in a user's profile in Slack.