Mix together the flour, salt, sourdough starter, butter, and herbs to make a smooth (not sticky) dough. If it's too sticky, add more flour a teaspoon at a time and incorporate.
Divide the dough in half, and shape each half into a small rectangular slab. Cover with plastic wrap, and refrigerate for 30 minutes -- or up to a couple of hours -- until the dough is firm. The starter is discard so there shouldn't be a whole lot of rising going on -- just getting that good flavor.
Preheat the oven to 375°F or 350°F Convection
Lightly flour a piece of parchment (soon to be two), your rolling pin, and the top of the dough.
Working with one piece of dough at a time, roll the dough out on a piece of parchment to about 1/16" thick. The dough will have ragged, uneven edges -- that's okay. Just try to get it even and the same thickness.
Transfer the dough and parchment together onto a baking sheet. Lightly brush with oil and then liberally sprinkle the salt over the top of the crackers.
Cut the dough into 1¼" squares (a rolling pizza wheel works well here). Prick each cracker with the tines of a fork.
Put in the oven and lower the temperature to 350°F or 325°F Convection.
Bake for 20-25 minutes until squares are browning at the edges. Midway through change racks and turn around to make them even.
When browned, remove from oven, cool on a rack, and store in an airtight container.