Add rice and popcorn kernels to Kitchen Mill, and grind into flour; set aside. Add ½ cup rice flour, yeast, sugar, and ½ cup warm water to WildSide jar and secure lid. Press "Pulse" 2 times, and allow yeast to proof for 5–10 minutes in warm place.
Line large baking sheet with parchment paper, and draw two 8" circles on it.
Add remaining ½ cup rice flour, corn flour, cornstarch, xanthan gum, and salt to clean WildSide jar and secure lid. Pulse 3–5 times.
In medium bowl, beat eggs lightly; set aside 1 tablespoon for brushing tops of flatbread. Add remaining 1 cup warm water and oil to beaten eggs. Add egg and yeast mixtures to jar with flour mixture and secure lid. Pulse 6–8 times, until ingredients are incorporated and dough ball forms.
Use spatula to spread soft dough into circles on marked parchment paper, heaping dough slightly in center. Cover loaves lightly with greased plastic wrap, and let rise until doubled in size, about 1 hour. Meanwhile, preheat oven to 425°F. Beat few drops of water into reserved beaten eggs, and brush over loaves. Dust lightly with rice flour. Use razor blade to slash tops of loaves into large diamond grid pattern (use up-and-down cutting motion rather than dragging blade through soft dough). Bake for 20 minutes or until well browned.