From this page of the Valheim guide, you will learn how to get your hands on Barley, which is useful in crafting.
Barley is one of the resources you can find as you explore the vast world of Valheim. Barley is used to make Barley flour, which in turn is used to make various foods and bread.
Barley can be obtained from Fuling villages found in the Plains biome. It can be picked up or cut down using a weapon. Harvested barley can also be used to plant and grow your own crops, but only on the Plains.