In addition to predefined approval groups, Knak allows you to send an email to an approver 'on the fly' for those situations where no pre-set approval group exists.
From the email creation screen select publish > send for approval
Select 'Add approvers' from the popup
Set up your approval workflow, add the stages you need and populate with approvers.
Hit send to activate the approval process.
Need more help? Contact support via live chat within Knak using the chat bubble in the bottom right corner or email firstname.lastname@example.org