Measure out dry ingredients into a mixing bowl.
Add the sourdough starter (it does not need to be in an active state), oil if using, and water.
Mix using the dough whisk, but don’t overmix; stir just until it’s combined. Depending on the thickness of your sourdough starter (its level of hydration), you may need to add a few more tablespoons of water or flour to get the dough to come together.
You can knead the dough on the counter a few times to get all ingredients incorporated.
Place the dough ball back into the bowl and cover with a towel.
Let the dough sit at room temperature for at least 30 minutes. Resting it for 5-8 hours will let the sourdough break down more of the phytic acid in the flour. The longer it sits, the more sour flavor your tortillas will have. For a less sour flavor, rest for five hours.
After the dough has rested, divide it into six equal balls of dough (or four equal portions for burrito or wrap-sized tortillas).
On a lightly floured surface, flatten the dough ball with the palm of your hand, then roll with a rolling pin to create a rustic circle. Turn the tortilla 1/4 turn after each pass with the rolling pin to help form a more uniform circle and to ensure the dough isn’t sticking to the counter.
Cook in a preheated cast iron skillet until golden brown on one side. How long this takes will be determined by how hot your skillet is – use a spatula to check for doneness after you see a few bubbles forming on the top of the tortilla.
Flip and cook on the other side until golden brown.
Remove from heat and transfer to a plate. Cover with a towel until ready to serve.
Best when served slightly warm.