Creating a Slack app that uses Webhooks to send messages to a channel
Create an app
Sending messages
Once you have the webhook URL, you can try it out by sending it sample data
curl -X POST -H 'Content-type: application/json' --data '{"text":"Hello, World!"}' https://hooks.slack.com/services/XXXXXX/YYYYYY/XyXyY123xxxY
This will post a fairly straight forward Hello, World! message to your channel
Customizing message layout
Block kit