Just make a tuck right above the original hem. The extra fabric will be to the wrong side of the leg. In order to stitch this tightly to the hem you will need to use your zipper foot. Cut off the excess and finish the seam to prevent ravelling.
Jacquie
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Ladysmith BC,Janome 12000, Bernina Record, Bernina 1150MDA serger, bit of a Luddite, garments not crafts