Add brown rice to Kitchen Mill, and grind into flour; set aside. Add popcorn kernels to Kitchen Mill, and grind into flour; set aside.
Add ½ cup rice flour, yeast, sugar, and ½ cup warm water to 2-cup measuring cup; mix. Let rest in warm place until doubled in volume, about 10 minutes.
Line large baking sheet with parchment paper, and draw two 8-inch circles on it (use cake pan as a guide).
In large mixing bowl, beat egg whites lightly. Add olive oil, olives, and 2 teaspoons rosemary; set aside. Combine egg yolk and garlic in small bowl; set aside. Combine remaining rice flour, corn flour, cornstarch, xanthan gum, and salt in large bowl. Add remaining ¾ cup warm water to egg white mixture, and stir into flour mixture. Stir in yeast mixture, and beat until smooth.
Using rubber spatula, spread soft dough into 8-inch circles marked on parchment paper, heaping dough slightly in middle. Cover loaves with lightly greased plastic wrap, and let loaves rise until doubled in size, about 1 hour.
Preheat oven to 425°F. Remove garlic pieces from egg yolk, and brush egg yolk over loaves. Sprinkle tops with remaining 2 teaspoons rosemary. Use razor blade to slash tops of loaves in large diamond grid pattern. (Use an up-and-down cutting motion rather than dragging blade through dough.) Bake for 20 minutes or until well browned.