I wasn't sure what to buy, so, knowing that the lady in question likes a 50s dress, thought I'd make her a circle skirt. I used the directions Casey posted in her sewalong to craft the size - using a 40" circle to give a likely hip (since I don't know the right dress size!) measurement, and sewed it onto a 28" band of elastic. This way the skirt can be pulled on and suits a good range of waist sizes!
To attach it to the waistband, I first overlocked the waist seam, and then pinned it to the inside of the elastic at regular intervals. Then I simply stretched the elastic till the fabric fell flat and zigzagged it on.
Simples! And it gives a nice even gather too!
While the maths was something of a challenge (working in a combination of inches and cms didn't help that), this was a breeze to make. I got to use my rolled hem foot and was pleased at how evenly the hem turned out. All in all, a great little project, and I'd strongly recomment Casey's sew along instructions to beginners.