First, mix together the flour, sourdough starter, olive oil, salt, nutritional yeast, and garlic powder to make a smooth, not sticky, dough.

Then, divide the dough in half, then shape each section into a small rectangular slab. Next, cover with plastic wrap, then place in the fridge for at least 30 minutes to help firm up the dough.

Meanwhile, preheat the oven to 325°F.

Then, remove the dough from the fridge, then very lightly flour a piece of parchment paper, a rolling pin, and the top of the dough.

Next, roll the dough to about 1/16" thick on top of the parchment paper; it will have uneven edges as you roll it out and that's OK. Just try to make the thickness as even as possible. Transfer the parchment paper with the dough onto a baking sheet, then lightly brush with more olive oil and sprinkle a little more salt on top of the crackers if desired.

Then, cut the dough into 1/1 1/4" squares then prick each square with the tines of a fork.

Then bake the crackers for 17-20 minutes, until the squares are starting to brown around the edges. Midway through, reverse the baking sheets: both top to bottom, and front to back; this will help the crackers brown evenly.

Finally, remove the crackers from the oven, and transfer them to a cooling rack. Store airtight at room temperature for up to a week; freeze for longer storage.