Because this is 100% untreated wool, you can't just chuck it in the washing machine, unfortunately. Either use a special wool machine wash, or preferably wash by hand in warm water. Don't use fabric softener!
Wring it out after washing inside a tea-towel to get rid of excess water. Reshape while damp, and dry flat if possible. To stop it curling up after drying you can steam iron back into shape using a wool setting.
