In a medium mixing bowl, whisk together tapioca starch, coconut flour, and sea salt. Set aside.
In a separate bowl, whisk almond or cashew milk with the egg whites until well-combined.
Make a well in the center of the dry ingredients and pour the egg white mixture into it. Whisk to combine. There should be no lumps and the batter will be very, very thin. Transfer the batter, if desired, to a large glass measuring cup with a spout, for easier pouring.
Heat a nonstick skillet over medium-high heat. (A well-seasoned cast-iron skillet or crepe pan works best.) Lightly oil the skillet--not much is needed, just a few drops.
Pour a few tablespoons of the batter into the center of the skillet, and working very quickly, lift the skillet off the heat and tilt so the batter spreads out in a thin layer. Depending on the size of the skillet, the batter may or may not reach the edge of the pan. Place back on heat and cook for 1-2 minutes, or until golden. It will be ready to turn when the tortilla has released itself from the pan. Gently lift the edges and slide a thin spatula underneath to flip. Cook the other side for another 1-2 minutes. Transfer to a plate and repeat with remaining batter.
Use as desired.