Combine sourdough starter, water, oil, and salt in a large mixing bowl.
Use your hand to gradually mix in the flour until a soft, slightly tacky dough forms. Avoid adding too much flour or the tortillas will be dry.
Allow dough to rest for at least 20 minutes. 8 hours or overnight fermentation will make them easier to digest.
Heat up skillet for at least 10 minutes on medium-high heat.
Divide the dough into 12 equal pieces and roll into balls. Divide into 9 pieces for larger tortillas or 18 pieces for small.
Roll out the first tortilla as thin as you can without tearing. Place in the skillet carefully.
Allow to cook for only 1 to 2 minutes on the first side, until large bubbles form. While it cooks, roll out the next tortilla.
Flip the tortilla and cook on the other side for only a minute. Remove and place on the cooling rack.
Cook the next tortilla, rolling out another one as before. Repeat the process of cooking one while rolling out another until they are all done.
Serve immediately warm or allow to cool and save for later.