I've gotten great feedback about this challah over the years. Using Blends by Orly Manhattan Blend to bake gluten-free challah gets you a perfect result every time.
This recipe has a percentage of oat content so that you can wash your hands and make a Hamotzi blessing on the challah. If you want to be able to say Bircat Hamazon (Grace After Meals) too, you have to make the flour content over 50% oats. See note at the bottom of the recipe for how to modify.