This might help...
Using ISE NAC you can setup a sponsor portal where you can have users register as a guest and it emails someone to approve it. That user then receives their credentials via email back to log on to the WiFI. The issue being if a user has no external access via 4G to receive the email credentials it can be cumbersome, plus employees have to approve them. ISE offers a few different variants including a pass through (no auth), and self-register by putting in some required details like a name and email address.
If you don't have ISE or can't use it, then on the WLC you can create a 'guest lobby' account which gives a user the ability to log on to the WLC and it will give them only the guest creation page. On there they can create the guest and provide the details to the user.
Ric
-----------------------------
Please rate helpful / correct posts