1. Start a Capture the Flag match with only you and no bots
2. Map - Desert (small)
3. Set time for max with no set number of Flags for the win
4. Make sure to holster your weapon to run faster
5. You don't have to wait to be teleported out of the start zone, run through the teleporter in the middle of the room to start immediately
6. Flags are on opposite, outside corners of the fort so you just keep running back and forth (short cut is through the hallway)
With no bots you don't have to worry about interruptions and will get in a good rhythm running back and forth.