Every feed leaves a jar of discard. These crackers are the quietest way to use it: a soft dough, a thin roll, and a bake until the edges go gold.
Unfed starter from the fridge is fine. The thinner you roll, the more they shatter. Rosemary or sesame is optional; flaky salt is not.
If they soften by the next day, a few minutes in a 300°F oven brings the snap back.