Mix your flour and salt in a large bowl, then cut your butter into the flour as best you can. A fork works well to do this. It doesn't have to be perfect as you will be kneading the dough by hand at the end. You want a shaggy dough to form that you can then blend together with your hands.
Add the starter and water to the mixture. Mix until well combined, you will probably need to use your hands at the end to make sure all ingredients are incorporated well.
Press your dough into a rectangle on a lightly floured surface and cut your dough into 12 equal sized portions with your bench scraper. I usually cut the rectangle in half, then each part in half again, then the remaining parts in to 3 portions to make 12.
Roll each portion into a ball, pinching the dough where there are any seams.
Cover and let the dough balls rest for at least 30 minutes. This is usually when I take care of making whatever else is for dinner.
Roll each tortilla out on a lightly floured surface (counter top or silicone baking mat). You want them pretty thin, this is what cooks the best. 6-8" tortillas are usually best.
Heat up your skillet. Medium-high to get it warmed up then lower it to medium low so you don't burn the tortillas. A hot skillet is essential to cooking the tortillas properly!
Cook your tortillas. This is the time consuming part because you can only do one at a time, unless you have multiple skillets going. You want to turn them after about 30 seconds to 1 minute or when they start to puff up and brown just a tad. Cook for 30 seconds on second side and transfer to plate.