Preheat oven to 350°F. Prepare 2 baking sheets with parchment paper. Set aside.
In a medium bowl add the flour, oil, and salt.
Pour sourdough starter over top and mix until all ingredients are fully combined.
Place combined ingredients onto a clean counter and gently roll into a smooth ball. Wrap in plastic and refrigerate for 30 minutes. (Up to overnight.)
After 30 minutes, remove from the refrigerator and cut in half. Rewrap one of the halves and place back into the refrigerator.
Take the dough and cut into 3-4 pieces. Lightly flour your counter. Now roll out each piece into as thin of a layer as you can. It does not need to be uniform in shape, just consistent in thickness.
On a baking sheet that is lined with parchment paper, lay out the pieces. I could fit 2-3 pieces on each baking sheet.
Brush each piece with water (not soaking it) and then sprinkle with sea salt.
Bake for 15-22 minutes. The cracker is done when it is crisp and browning.
When done remove from oven. I let mine cool right on the pan. If you want to reuse the pans for the remaining crackers, move the cracker sheet to a cooling rack.