Combine the rice flour, tapioca flour, baking powder, baking soda, and salt in a large bowl and stir with a whisk.
Combine the soymilk, oil, ground flaxseed, and maple syrup in a medium bowl and mix thoroughly.
Pour the liquid mixture into the flour mixture and stir until well blended, and any large clumps of rice flour are gone.
Let the waffle batter stand for 3 to 5 minutes while preheating a waffle maker according to the manufacturer's directions. This will allow the rice flour to absorb a bit more of the moisture, and will allow the flaxseed to thicken the batter a bit.
Stir the batter a bit more if necessary to get rid of any remaining rice flour clumps.
Spray both grids of the waffle iron very generously with oil. (See note.) Pour or ladle the batter onto the center of the iron. As this batter is relatively thin, it should spread all the way out to the edges. If the first waffle is either too small or significantly overflowing, just adjust accordingly for subsequent waffles.
Bake each waffle for 3 to 5 minutes, or until it can be removed easily, spraying both grids generously with oil prior to each waffle.