Gluten Free Flour Mix
From America's Test Kitchen

If you have a scale it is better to use it so I will put both weights and measures in case you don't.

24 oz (4 1/2 cups plus 1/3 cup) white rice flour
7.5 oz (1 2/3 cups) brown rice flour
7 oz (1 1/3 cups) potato starch
3 oz (3/4 cup) tapioca starch
3/4 oz (3 TBSP) nonfat milk powder

Whisk all ingredients together in large bowl until well combined.  Transfer to airtight container and refrigerate for up to 3 months... I use it faster so I don't refrigerate it... If you are not going to use it faster freeze it....