Barley flour

Barley flour has a natural maltiness in flavor, and is low in gluten. Speck recommends letting doughs and batters made with barley flour (and, actually, all whole grain flours) sit overnight. The rest period will soften the bran, make the product easier to work with, and round out the flavors.
Best for: Barley’s malty-sweet flavor makes it ideal for sweet baked goods and cookies.
Do Not Use For: As with other alterna-flours, 100% barley flour does not make for an ideal bread.