Because I am that nice, I did a tutorial along with it:) There will be some simple math involved for you to get the right size, but I promise it will be worth it!
You will need fabric that you love, elastic, and matching tulle
You will be using 1/2 inch seam allowance unless otherwise stated.
First measure the child's waist and add one inch. My daughters waste is 18 inches. I wanted the length to go just below her knees so I measured from her hip to her knee and added 3 inches, which was 13 inches.
Now cut a piece of fabric using your measurements. My piece was 18 X 13. Cut a piece of elastic that is 1/2 smaller that the waste measurement.
Fold skirt in half. My piece was now 9 X 13. With RST sew down the width of skirt.
To make the casing for the elastic, fold over the top 1/4 inch and press. Fold over again 1/2 inch and press. Sew around the entire skirt, leaving opening for elastic. (Note: I use the salvaged edge so I didn't have to fold over twice)
To insert elastic, attach to a big safety pin and thread through the waste.
Sew the two ends of the elastic together once threaded through. Make sure elastic isn't twisted. Sew opening closed where you put elastic through.
Cut a piece of tulle that is double the length you want it to be. I cut mine at 6 inches so there will be 3 inches of tulle peaking out. Fold your tulle in half.
Now comes the fun part. Set your tension to the highest setting. Set the stitch length to it's longest length. Using a 1/4 inch seam allowance, sew the length of the tuile. The machine should do all the ruffling for you!
Attach the tulle to the inside of the skirt, with fold facing toward the bottom of skirt.
Now, top stitch around the bottom to prevent the tulle from flipping up.
Put the skirt on your little person and go take pictures.