The Advanced Form Integration plugin allows sending messages to specific Slack channels from many popular WordPress forms or when an WooCommerce order is placed.
Create a Slack app
Go to the Your Apps page. Click on the Create New App button. Select the option to setup it from scratch.
Insert an app name as you like. Select the Workspace where the channel exists.
Now the app page will open. Go to the Incoming Webhooks menu. Turn on the button to activate incoming webhooks. Click the Add New Webhook to Workspace button.
Select the channel where you want to send the message automatically. Then click the Allow button.
Copy the incoming webhook URL.
Create a new AFI integration. In trigger section select the form provider and the form itself. In action, select Slack. Select Send Channel Message as the task. Paste the webhook URL that was copied in the previous step. Now setup the message section. Finally save the integration and you are don.