Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Bakersfield to Fayetteville as you normally would.
These are just IATA (International Air Transport Association) codes. They are used in aviation to identify and differentiate airports. That’s why a Bakersfield Meadows Field Airport to Fayetteville Northwest Arkansas Airport flight would often be abbreviated as a BFL to XNA flight.