For the self-service flow to be triggered, you will need to switch the 'editing' permission for the relevant category to off. Employees will still be able to edit the information, but this action triggers the self-service flow.
Should you be testing this out, please note that as an Admin, your permissions are by default that you will always have the edit function in your 'Admin' group therefore this will not be able to be applied to you:
*Note: Anyone with editing permissions can edit the categories regardless of the flow settings. Flows are not triggered for these users who have edit permissions to all of the categories included in the flow. For this reason, Admins cannot use self-service flows.*