I used double strands of Caron One Pound yarn in Dark Grey Mix. I’ve never made anything with any kind of structure just by crocheting! It was a fascinating process. Essentially, it was almost entirely single crochet all the way around and through the thing! Unfortunately, my poor Addi Swing hook broke due to the force I had to use to work the double strands. The metal shaft totally detached from the plastic handle. Fortunately, the manufacturer exchanged it for me free of charge.
If I decide to make another one, I would use more than one color. I like a charcoal gray as much as the next person, but it gets kinda boring after awhile.