Don't do this. Take the flaps off and work on them off the aircraft. Tried to do something quick. It's costing me much more time now to fix it. Do it as per the manual. Went to the hanger this morning with 4 plies of 32" x 6" BID and epoxy to create the first layup of flap root extensions. Thought it would be easier if I just left the flaps on the wing. Covered the foam cores with peel ply. Laid up 2 plies BID on a sheet of poly and applied them, with much difficulty, to the flap root. Used a spring clamp to attach a mixing stick under the flap root to hold up the end of the layup. Applied tape where necessary to hold it all in place to cure.