Last summer, I bought this white maxi from H&M knowing I'd shorten it. I've never been able to find a white midi skirt I liked and thought the embroidery at the bottom of this skirt was interesting.
I followed the slight curve of the design. Even if the skirt you use doesn't have a pattern, I'd still recommend cutting it off with a soft curve so the finished product will look more organic and natural.
I left the remaining length of the underskirt to serve as a built in lining (which I also hemmed) since white is easy to see through.