Application insights slack integration
You may have a look at this link: https://github.com/Azure/azure-quickstart-templates/tree/master/201-alert-to-slack-with-logic-app. I followed the instruction and it worked for me.
The tricky part is you need to click the "Deploy to Azure" button on this link page. It would redirect you to Azure Portal, and you will need to specify which channel you want the alert message to be sent e.g. #somechannel. Don't use direct message like @yourname, it has some problem with that and the logic app couldn't deploy for me.
Then you just follow the instruction to find the deployed logic app and authenticate it by logging into slack. And you also need get the logic app URI from the deployment output as in the instruction. Once you put the URI into the alert webhook, you are ready to go!
It's relatively easy to set up a slack webhook.
There's a pretty good C# nuget package for this at https://github.com/nerdfury/Slack.Webhooks
Although you'd need to set up a seperate service to poll and route the app insights data.
There's also commercial options.
getcloudbot.com allows you to hook your Azure Application Insights bundle directly into your slack channel. It's good at staying on top of your services. Disclaimer : I run it.