Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Distraction
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Overcame Equipment Problem; Flight Crew Rejected Takeoff
Human Factors; Environment - Non Weather Related
I was on short call. The crew desk called to assign a 1 day pairing. I woke up and got ready for my deadhead to ZZZ.Once in ZZZ the Captain called operations to find out how we get to SPOT X. Operations mentioned the plane was in Maintenance and it might be a few hours until it was ready. After about :45 minutes Maintenance deferred the R FMC. We received a new release and were taken to the aircraft. Once onboard we both did our normal flows. I also used the FERRY Checklist.We were slightly out of our normal flows and the right FMC was deferred. Once we completed our checklist Maintenance cleared us to start the engines. I started both engines per SOP. The L ENG was a no start. I followed the ECL and contacted Maintenance as instructed by the FM. Maintenance had us restart the L RNG and there were no issues. The Captain called for 'Flaps 5; After Start Checklist. Somehow doing my flow after start flow I set Flaps 1 instead of Flaps 5. We taxied from the Maintenance Hanger to Runway XXL. We completed all of the Checklist. A note: with the right FMC deferred the LWR CTR DU can be used via Display Select Panel (DSP) i.e. ENGCOMMCHKL displaying only one at one time.Taxi was normal and all checklist completed. The Captain was PF and on the application of takeoff power the TO CONFIG Master Warning went off for Flaps. The Flaps were set to 1 not 5. We pulled off the runway and notified Tower. I ran the rejected TO checkout and we taxied back to XXL. The Captain and I discussed how could we have missed that? I set the flaps to 5 and re-ran the Before Takeoff. We checked the brake temps and the FMC and briefed our departure again.Once in cruise we debriefed how we missed such an important item. For my part it is not lack of proficiency; I just flew an trip as PF. Some factors that might have affected me were: the early call; the FMC deferral and the Engine no start. Also; with COVID-19 there are so few flights and we had a tight window to make the only ZZZ2 flight from ZZZ1 today. This self-induced time pressure might have subconsciously contributed.
First Officer reported setting the incorrect flaps resulting in an immediate rejected takeoff after receiving a configuration warning.