Hello, I'm currently doing a flight from KAVX-KSEZ. KAVX is uncontrolled, how do I go about requesting IFR clearance since there's no clearance delivery, ground etc? I tried selecting the local approach frequency and hitting hot key 0, but that did nothing. I then tuned the unicom frequency and announced I was taking the runway, thinking I could contact approach in the air and request clearance. After take off, approach is not talking to me, I've tried hitting the 0 key, even the 9 key to report my position and I get no response. I'm hearing no chatter to AI aircraft despite flying through busy Los Angeles airspace.
What would have been the correct way to start this flight?