Directions

1. Stir together sourdough starter discard, cornmeal, flour, seeds, kosher salt, and 2 tablespoons of the oil in a medium bowl. Knead gently just to bring dough together. Divide dough in half, and shape into two (about 4-inch square) bricks. Wrap each brick tightly in plastic wrap; chill until firm, at least 30 minutes or up to 3 hours.
2. Preheat oven to 350°F. Cut a sheet of parchment paper to form an 18-by-13-inch rectangle; lightly dust with flour. Unwrap 1 dough brick, and place on prepared parchment paper. Lightly dust top of dough brick, and roll to a 14-by-12-inch rectangle, about 1/16 inch thick. Brush top of dough rectangle with 1 1/2 tablespoons of the oil. Sprinkle with 1/4 teaspoon of the flaky sea salt (or more to taste), and optional toppings.
3. Using a pizza cutter or a chef’s knife, cut dough rectangle into roughly 1 1/2-inch squares. You’ll have about 60 squares. Carefully slide parchment paper with dough squares onto a baking sheet. Bake until crackers are golden around edges, 18 to 24 minutes, rotating baking sheet 180 degrees halfway through bake time. Transfer baking sheet with crackers to a wire rack; let cool completely, about 30 minutes. Meanwhile, repeat process with remaining dough brick, oil, flaky sea salt, and flavoring sprinkles.