In a medium bowl, whisk together the cassava flour, fine sea salt, baking powder, and any optional dry add-ins (garlic powder, dried Italian herbs, black pepper, ground flaxseed). Make sure the baking powder is evenly distributed.
1 1/2 cups cassava flour, 1 teaspoon fine sea salt, 1/2 teaspoon baking powder, 1 teaspoon garlic powder, 1 teaspoon dried Italian herbs, 1/4 teaspoon black pepper, 1 tablespoon ground flaxseed
Drizzle in the olive or avocado oil. Use a fork or your fingers to rub the oil into the cassava flour mixture until it resembles slightly damp sand.
2 tablespoons olive oil or avocado oil
Pour in about 3/4 cup of the warm water (and apple cider vinegar if using). Stir with a spoon or spatula; the dough will look shaggy at first. Add more warm water 1 tablespoon at a time until the dough comes together into a soft, smooth ball. It should feel like play-dough—pliable but not sticky. If crumbly, add a bit more water; if sticky, sprinkle in 1–2 teaspoons more cassava flour.
1 cup warm water, 1 teaspoon apple cider vinegar
Cover the bowl with a towel and let the dough rest for 5–10 minutes to fully hydrate and reduce cracking when you roll or press it.
For flatbread or tortillas, heat a cast-iron or nonstick skillet over medium to medium-high heat. For pizza crust, preheat the oven to 425°F (220°C) and place a sheet pan or pizza stone inside to heat.
Turn the dough out onto parchment paper or a lightly floured surface (use a light dusting of cassava flour). For flatbread or tortillas, divide the dough into 6–8 equal pieces for smaller rounds or 4 pieces for thicker ones. Roll each piece into a ball, flatten with your palm, then roll or press into a 5–6 inch circle. For pizza crust, roll or press all (or half) of the dough into a 10–12 inch circle or rectangle on parchment, about 1/4 inch thick.
Working one at a time, place a dough round into the hot dry skillet. Cook 1–2 minutes, until bubbles form and the underside has light golden-brown spots. Flip and cook another 1–2 minutes. For softer, wrap-style tortillas, keep the bread lightly colored and stack cooked pieces in a clean towel to steam. For heartier flatbread, cook until more deeply browned but still soft in the center.
For pizza crust, transfer the rolled dough on its parchment to the preheated sheet pan or stone. Bake 8–10 minutes, until the edges are set and just turning golden. Remove, add sauce and toppings, then return to the oven for another 8–10 minutes, until the toppings are cooked and the crust is browned around the edges.
Break off a small piece of cooked flatbread and taste. If needed, sprinkle with a bit more salt or brush with olive oil and garlic while warm.
Serve the cassava flour flatbread warm. Use as a side with soups and stews, as a wrap, as soft tortillas, or as a base for pizza or sweet toppings.