put the left shifter into the small gear position. de-attach cable from FD, take up slack and reattach.
the shifter won't wind up any more cable than what's limited by the FD and you won't have a drooping cable when the cable is released.
+1 Basically you first adjust the inner limit screw to position the fd properly over double's small chainring.
Then set the shifter to shift between the granny and the middle ring positions but you use the new inner ring as the granny and the big ring as the former middle. That way the high limit screw keeps you from moving the shifter and fd any further and locks out the extra click.