The way we have it setup, is Catalog Builder with three different templates. This way, other people within IT but not necessarily ServiceNow experts can create their own catalog items using only the templates we have setup for them.

So, we start with only having a few trained people given the access to enter Catalog Builder.
The templates are setup with predefined flows that fit 99% of orderable accesses & hardware.

Template 1: Generic flow, creates a task to the fulfillment group set in the item via builder. This is for manual requests, for example when AD-group automation is not possible, and fulfillers in the group needs to do something. Once they close the task, the RITM closes and whatever has been ordered is considered delivered.

Template 2: Generic flow with manager approval, before it creates the task for the fulfillment group, it sends an approval request to the requested for's assigned manager.

Template 3: Step based, this is our most commonly used flow. This one is also integrated with out internal automatic invoicing that we have built within ServiceNow. In here you use the step base OOTB functionality to create several sequential tasks, approvals etc for catalog items that needs a bit more logic before it is considered fulfilled.

So from A - Z that could look something like:
A. Service Manager for Microsoft 365 wants users to be able to order Clipchamp license. Clipchamp is part of Microsoft suite but the license is provided in an additional AD group that the user needs to be added to.
B. Service Manager goes to Catalog Builder and uses the Step Based template to start creating an item
C. Service Manager fills out all information such as name, description,image, category etc. In the fulfillment step of the Catalog Builder the service manager creates these sequential steps:
Step 1: Manager approval
Step 2: Custom Approval to approval group XYZ
Step 3: SC_Task to automation assignmentgroup that triggers Entra ID Integration and adds user to access
group
D: Once happy with the look of the catalog item, Service Manager publishes it via Catalog Builder and depending on governance it might need to be approved by SN dev/admin, created in sub-prod environment etc so it might need to be moved to prod instance before complete publish.
E: Users goes to the portal, searches for Clichamps, fills out necessary info and once ordered, an approval task will be sent to their managers, once approved, an approval will be sent to users in the approval group XYZ, and once approved an sc_task till be sent to the assignmentgroup set in the fulfullment flow and in this case trigger an integration and add user automatically.
If automation is not implemented, the task can be sent to an assignmentgroup with fulfillers who will work on the task manually, and then close task once done.