A couple readers had a question about how I created the boxed shape to fit the sides of the footstool, so I thought I would post it here should anyone else be wondering the same.
I worked the top according to Peggy Adamik's "How to Crochet a Granny Rectangle". When the rectangle became the same size as the top of my stool, {or whatever you may be making a cover for}, I stopped making the extra 3 double crochets in the four corner spaces--in other words you will now make 3 doubles and 1 chain in each and every space all the way around. Now the rectangle will not become any larger, but will form the boxed sides of your cover. I found I needed to snug up the sides of my cover a bit, so I did a round or two with 3 double crochets in each space and left out the 1 chain--this helped make the sides a little tighter as needed. Just try on your cover after each side row to see how it fits and adjust if needed.I hope this is helpful. If you're crocheting a cover or have made one already, I would love to see a picture of it!