Alerts are set up in Build list and in editor. The slack and email settings are under the Alerts button on build list, the per interface settings are in the editor under the Alerts button, the per step settings are on the form of the steps.
Checkboxes below if selected alerting is on by default, if alert or is set.
Alert me when:
On App alerts settings (in build list) there are
Per interface:
Per step (hide this behind an alerting checkbox, like we had for debug etc):