We were given some clothes from a friend of ours and M. found a skirt in the stash that she wanted, of course. However, it was a tad too short for her comfort zone. So we used Emily's eyelet slip extender idea and transformed that skirt for her so that she can now wear it comfortably.
Our slip is not separate, but I sewed it right into the waistband. I happened to use some eyelet lace curtains that had been given to me that I wasn't going to use as curtains and then just used that fabric to make the slip. I needed to adjust the elastic waist anyway and so that is why I did this way. She is happy with how it turned out and now she can enjoy this cute embroidered skirt for the remainder of the summer.