First, you’ll want to find a large (ideally thrifted) skirt. The only requirements are that it not cost a whole lot, you love it, and hopefully it already has a seam running down the back. I have done this to many skirts that don’t have a back seam, so it’s not required.
As you can see, the skirt I picked was cotton (easy to sew with), used a busy fabric (no need to match patterns up), and had an elastic waist. It also had a seam up the back. These qualities all make it the BEST kind of skirt to quickly alter. The only thing that didn’t make it absolutely perfect for this project was that it had side seams as well. Those side seams will shift towards the back a bit when you do this alteration, so if you can skip them or modify it by taking in the sides rather than the back, your skirt will turn out the best.
First, try on the skirt and find out how much excess fabric you have in the waist. You’ll want to pinch it and then pin it in the back. If you try the skirt on inside out, you won’t have to move the pin when you go to sew. Then try it on after you have pinned it to make sure that you can still pull the skirt up and down to get it on and off.
Next, make sure the skirt is inside out and pin all the way down from the waist in the back. (If you had only side seams you could also split the difference of the excess fabric and pin down each side of the skirt.) You will be taking the seam in, so whether you do it in the back or on the sides doesn’t matter. Depending on the shape of the skirt, try to just pin the same width away from the original seams as possible.
I probably alter ten skirts a year like this, and it’s one of my favorite ways to alter clothing. It isn’t a perfect job, but it works, it’s quick, and these are the kind of inexpensive and fun skirts that you can wear a few times and then re-donate.
Have you tried this kind of alteration before?