Good luck with that one!!! Most falconers are reluctant to share this type of information with others, especially those they don't know or know well. Besides, this is one of the important parts of falconry and you should have been looking before now. In fact, I started looking a full year before I got my first bird.
Just drive round and look for land thats not been built on or part of a housing complex. Look for dumping ground with stone and concreate mounds on or waste land.
Oklahoma Falconers are very touchy about telling people where they hunt.
Look for public land , might mean traveling out side of OKC at the weekends and then find a couple of local fields for durring the week.