I would suggest go with Prometheus operator, as this project is cloud-native and give good hold on managing the alerts.

• Handles alerts with alert manager

• We can add data source with Grafana

• Write our own expressions for pod and microservices monitoring

• Works on scrapping over http/s request

• we can easily expose the Applicaton metrics

https://github.com/coreos/kube-prometheus

Kubernetes dosn't provide out of the box slack integration.

There are few projects that you can use:

• https://hub.kubeapps.com/charts/stable/kube-slack - runs on Kubernetes, watches for evnets and sends pod failures notifications to Slac

• https://hub.kubeapps.com/charts/stable/kubewatch - similar project. depending on configuration can be quiet noisy

If you need more complex motoring you can use Prometheus and it's alert manager https://prometheus.io/docs/alerting/notification_examples/