
I used my rotary cutter and ruler and just cut straight across the dress right below the stain.

The dress has a lining, so I did a basting stitch to keep the lining together with the dress and then zig zag stitched along the cut edge to keep it from fraying. Then I folded the top edge in about an inch and stitched along the edge to made a casing for the elastic. Just make sure to leave a few inches open so you can thread the elastic thru.

Once the elastic was in, I stitched the last couple inches of the casing closed and the skirt was complete.

The skirt ended up being longer than the original dress was, so you could also do this with a dress that has grown too short. Just cut the dress across right below the arm holes, make that the waist and it will give you a few extra inches.