You can delete a message in Slack using the Google Now app on your phone or tablet.
The Google Now settings page is located under Settings > General > Google Now.
Open the app, then tap on the “Delete” button.
To delete a tweet, tap the green Delete button in the message field.
To use Google Keep, tap on “Keep,” then tap “Delete.”
When you delete a notification, it will appear in the “Done” section of the app.
To cancel a notification from the Google Keep app, tap it, then select the message you want to delete.
To clear the list of recently deleted messages, tap “Done.”