Some yarn winders wind the yarn into a configuration known as a "yarn cake."
Yarn cakes vary in shape, but they are typically shaped something like a cylinder – or, you guessed it, a cake. The top and bottom of the cake are often more or less flat.
Yarn cakes are easy to store; they can be stacked on top of each other easily. They are also easy to crochet with.
Kate's grandma has a yarn winder, so she brings her skeins of yarn over to Grandma's house to make yarn cakes.
Janet stores her yarn cakes stacked on top of each other to save space.