This feature is no longer available in Canvas. Please see Canvas Release Notes (2019-10-19)
Users with Slack admin rights can create and install a Slack App to create a Bot Access Token to enable Canvas notifications for all users within a workspace.
After the bot is created and verified, individual Canvas users can enable Slack as a Canvas contact method to receive notifications.
Create Slack App
Slack admins must create a Slack API key from Slack admin settings to enable Slack for all users in the workspace. To create a Slack App and API key, log in to your Slack account. Then visit the Slack Apps page: https://api.slack.com/apps.
Click the Create New App button. In the Create a Slack App window, create a name for the app, which will display to users in the Slack workspace (such as Canvas notifications or Canvas bot). In the Workspace menu, select the workspace where the app should be enabled (i.e. the name of your institution).
Add Slack Bot Access Token
Once the app is created in Slack, click the Install App link. Locate the Bot User OAuth Access Token and click the Copy button.
In Canvas, return to the Account Settings page. Locate the Slack API Token heading and paste the token in the New Slack API Key text field. At the bottom of the Account Settings page, click the Update Settings button.
Note: If the Slack API Key heading is not available, refresh your browser window and try again.
Create Canvas Contact Method
In the User Settings page, click the Contact Method link. Select the Slack Email tab, and enter the email address of your Slack account. Click the Register Slack Email button.
Confirm Communication Channel
In Slack, look for a notification sent to the newly created Slack App with a four-digit Canvas registration code.
In Canvas, enter the code into the Confirm Communication Channel window. Click the Confirm button.
Verify Contact Confirmation
Verify your account has been confirmed.
All users in your Slack account can now add the Slack Email contact method in the User Settings page.
If you want to enable Slack notifications for your own account, view your User Settings Notification Preferences page. Locate the Slack notification type; by default, all notifications are turned off and any notifications must be enabled individually.