Hats aren't the first thing you think of when you think layering. Layering traditionally means tossing on a jacket over a dress. But if you wear a beanie, layering hats on top of each other is easy.
This is best done when you are wearing beanies that are made up of two different textures. Wearing multi-textured clothing helps your outfit look more expensive, and gives you some variety. It's cool two see two obviously different fabrics on top of each other.
Wearing two layers of hats will also keep you extra warm. You will not need to utilize ear muff. You can create patterns by pushing back one beanie to expose the other, or choose one with a "net" design so the other beanie shows through.