First, measure around the waist. My daughter is a size 10, her waist is 26. Then measure the hips. If it is for a child, it might be the same as the waist, Evie's was 29. Then measure from the waistline to where you want the skirt to hit. Our measurement was 20 inches.
Since this is elastic waist and not fitted, it doesn't have to be perfect. You need at least 12 inches more around than your largest measurement (hips or waist), so I cut a piece of fabric 44 inches wide by 20 long. The more you add the fuller the skirt. Yes, I rotary cut. Then I cut 2 pieces 44 inches by 4/2 for the ruffle. You need about twice as much width in the ruffle to make it full.
For the French seam, fold the skirt so the 20 inch ends are together and wrong sides are together. Stitch at a scant 1/4 inch seam. Trim it to 1/8 inch, then take it to the ironing board.
turn it to right sides together and carefully press the seam. Then back to the machine.
Stitch a 1/4 seam right sides together. This encloses your original seam to prevent fraying. Cool, huh? I love french seams now!
So now you have a giant tube.
For the the ruffle, take your two pieces of 4 1/2 inch strips and sew the ends together to make one long strip. Then, bring the other ends together and sew to make a big loop.
Take the loop to the ironing board and fold in half, wrong sides together.
press seams open while you press the look in half.
take to sewing machine and topstitch around the fold. Then at the raw end, start at one of the seams and do a long gathering stitch to the next seam. Do a second gathering stitch from the second seam back to the first, so you will gather twice, once for the front and once for the back. It's just easier. start by pinning one of the seams from the ruffle to the seam of the skirt right sides together, then take the other seam of the ruffle and pin it to the opposite side of the skirt (there isn't a seam, so estimate). Then gather ruffle pinning as you go.
Once gathered and pinned, take to the machine, go back to a regular stitch and stitch down.
Press seam towards skirt, then go back and topstitch. This will keep the ruffle down and also help prevent fraying.
Fr a roll over waist, at the top end of the skirt press down about 1/2 inch all the way around, then fold over again about an inch (less if you use smaller elastic). Stitch around at the bottom to make a tube for the elastic, leaving about a 2 inch gap.
Cut your elastic about an inch less than the waist measurement. Using whichever tool of your choice, bring elastic through waistband.
Once through, stitch elastic together. I overlap it by about and inch and go vertically and diagonally a few times. Then work it through the waistband, and stitch the opening closed.
All Done!! Super Easy, huh?