Basically the author added shapes that would be cast into the stool. Clever idea. Not so sure about his claim as to the “cost” of $5. The dowel rods are like $10 alone. $1 for the bucket. And anotehr $5 for the cement….looking more like $20-25 to me.
http://www.instructables.com/id/DIY-Remix-Koi-Fish-5-Bucket-Stool-DIY/