Gluten Free All Purpose Flour Recipe - Version 2

I use this GF All Purpose Flour for cookies.

2 1/2 c Brown Rice Flour
2 c White Rice Flour
1/2 c Cornstarch
3/4 c + 2 Tbsp Potato Starch
3/4 c + 2 Tbsp Tapioca Flour
3 Tbsp Xantham gum