I began by measuring 10 inches down (you can choose whatever length suits you) and ripped across the bias. I finished the edges of the broadcloth, turning it in twice and doing a simple stitch, backed at the edges.
I then did one basting stitch across the unfinished top and gathered it in. I did two seperate pieces, one for the front and back and had them overlap at the seams so there is a slight slit on each side. I turned the top under when I sewed it to the dress, using an already existing seam at the bottom and sewing the piece with the dress overlaping, rather than both seams together.
Finally I cut a rectangle and folded it in half sewing across the fold to give it a more finished look. I turned the dress inside out and pinned it, then turned it right side out to sew again across the existing seam for the neck line. (It was a bit low).
Voila! A new dress- well new to me since I had to stop wearing it for a while because I washed it and lost a little length.
I also did it to my college graduation dress that I had the same problem with. Except this time because of the more prominant gather at the empire waist, I simply sewed the material in-seam with the dress because I didn't want it to be too puffy. Huzzah! Oh, and this was my very first project since High School, and that was, well, forever ago. My handy dandy mom came down to 'remind' me how to thread the machine, etc. Wow, good times.