I need to create multiple base URL slugs how?

I own 40 domains. All of which are re-directed to sub pages of my main site. I bought them so I could have a base url slug that’s unique to that page, for affiliate links. For example instead of only using http://www.thebrawlnetwork.com/fanatics I bought all our subpages. So I want to use http://www.bearsbrawl.com/fanatics, http://www.jetsbrawl.com/fanatics.
When I change the setting to be able to use short code URL. If I change that one my site to one of these, it defaults and changes all my pretty links to the new shortened base URL code. Instead of letting me just go back and forth continually changing and updated those individual codes.
How can I change the base URL slug to several, completely different but real urls I own?

I.g. Instead of only http://www.thebrawlnetwork.com/
http://Www.bearsbrawl.com/
http://Www.jetsbrawl.com/
http://Www.ravensbrawl.com/
http://Www.ramsbrawl.com/
Etc