To a non-reactive bowl add 1 cup of flour, 1 cup of sourdough starter (or discard), ¼ cup of olive oil, 1 tablespoon of fresh chopped rosemary, and ½ teaspoon of salt.
Mix all the ingredients until you have a smooth dough that is not sticky. If it is still sticky, you can gradually add a bit more flour until it comes together.
Loosely cover the dough and let it rest in the refrigerator for at least 30 minutes or up to 2 hours.
Preheat your oven to 375˚F.
Take the dough out of the refrigerator and with a rolling pin, roll it out on a silicone baking mat as thin as possible. Lifting and turning the dough every so often will help getting the dough very thin. Don't worry about uneven edges. If you don't have a silicone mat, you can use parchment paper, too.
With a serrated pastry cutter or simply a knife, cut the dough into long strips. Then cut the dough perpendicular to make squares or rectangles.
Using a fork, prick each square or rectangle twice. This will allow air to escape during baking. Otherwise, your crackers will look like little pillows.
Place the silicone mat on a cookie sheet, place it in the oven, and bake for 20-25 minutes or until golden brown.
When done, remove the crackers from the cookie sheet and let cool down. For best results, we like to store the sourdough crackers in an airtight container.
Enjoy plain, with some homemade butter, hummus, cheese, or your favorite spread!