This alteration to the skirt pattern is very simple because the Sarah dress has a seam at the waistline and that makes it much easier to change the skirt without affecting the fit of the body.
You may not know it but a gathered skirt like the one you see in the picture is simply a rectangle of fabric gathered and sewn at the waistline.
Measure the waist contour of the body pattern and cut two rectangles of fabric to make the skirt.
How long should the skirt/rectangle be?
The length of the skirt is up to you. Measure from the waist to the leg length you want. For example 75 cm for a midi length.
How wide should my skirt/rectangle be?
Again this is up to you. The wider your rectangle is the more gathering it will have.
Imagine your waist is 72 cm. You can multiply the waist x 2 to have a nice amount of gathering or you could multiply x 3 to have a lot of gathering.
Example 72 x 2 = 144
Rectangle of 144 x 75. One for the front and one for the back.
If the width were much larger you would have to cut several rectangles and join the pieces together on the sides as the width of the fabrics would not be wide enough to cut the skirt in one piece.
As the closure of the dress is in the back, the rectangle of the back will be divided in two, with a seam in the center to be able to sew the zipper.
That said, you can sew all the pieces together on the sides.
Gather the entire waistline on the skirt and sew it to the waist of the dress. Distribute all the gathering well so that the volume is well distributed and beautiful.
Once the skirt is attached to the body, the process of sewing the zipper is similar to that of the original Sarah dress. You can also finish the bottom of the skirt with a hem.
See you soon!