ACR FLC ABORTS TKOF DUE FLAP WARNING.

Narrative

THE FO FAILED TO SET THE FLAPS TO TKOF POS. I FAILED TO CATCH THIS. THE TKOF FLAP WARNING SOUNDED AS I ADVANCED PWR FOR A ROLLING TKOF. WE ABORTED THE TKOF; RECONFIGURED; AND TAXIED AROUND FOR A NORMAL TKOF. ON THIS FLT WE HAD MYSELF; A SENIOR FO; AND AN EXPERIENCED INSTRUCTOR; IN THE ACFT TYPE; IN THE JUMP SEAT. SHORTLY AFTER INITIATING THE TAXI CHKLIST WE HAD A TAXI CONFLICT. OUR TAXI INSTRUCTIONS WERE 'TAXI TO RWY 14L.' THERE WERE NO RTING INSTRUCTIONS GIVEN; DUE TO TAXIWAY REPAIR IN PROGRESS AT IAH OUR TAXI OPTIONS WERE COMPLICATED. AFTER TURNING ON TAXIWAY NB; PARTIALLY CLOSED; ENRTE TO NG; THEN THE N RAMP; WE NOTICED AN LGT HEADED WHAT SEEMED TO BE HEAD ON AT US TURNING ONTO NG FROM THE N RAMP. WE STOPPED AND CALLED GND CTL FOR INSTRUCTIONS. WE WERE TOLD TO CONTINUE AS THE LGT WAS GOING TO TERMINAL B AND NOT ONTO NG. THE FO CONTINUED THE TAXI CHKLIST FROM THE POINT HE HAD BROKEN IT. HE SKIPPED THE FLAPS ON THE CHKLIST WHEN HE RESTARTED AND DUE TO COMS WITH GND AND THE FLT ATTENDANT SIGNAL HE WAS READY FOR TKOF I FAILED TO NOTICE THE OMISSION. WE SHOULD HAVE STARTED THE CHKLIST OVER SINCE WE HAD NO METHOD OF MARKING; WITHOUT DOUBT; WHERE WE STOPPED. NONE OF THE 3 OF US NOTICED THE OMISSION; DESPITE STRICT STERILE COCKPIT PROCS DURING THE APPROX 15 MIN TAXI AND WAIT FOR TKOF. RIGID USE OF PROPER CHKLIST PROTOCOL WOULD HAVE PREVENTED THIS SITUATION.