1. Cut off hood, sleeves, and make the sides straight like below. See the right side? I haven't cut it yet, where on the left I have.
2. You will have 2 pieces of skirt body now.
Place body pieces right sides together and sew along ONE side to join. Press seam flat.
If you want to, you can serge- but it's not needed as knit fabric doesn't fray. Set aside for now.
3. Cut open one sleeve along the seam line and lay flat.