Combine all the ingredients to form a dough ball, taking care not to overmix. Einkorn flour absorbs liquid more slowly than regular flour, so the dough will be crumbly at first but resist adding extra water. The goal is a firm, non-sticky dough.
Place the dough in a bowl and cover tightly with a lid or plastic wrap. Allow it to ferment at room temperature for 8 hours. While the dough will rise slightly, it won’t double in size. When the dough is ready, chill it the in the refrigerator for 30 minutes.
Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
Roll out the dough to about 1/8-inch thickness. Use a goldfish-shaped cookie cutter to cut out the crackers. Place the cut-out crackers on the prepared baking sheet. If desired, sprinkle the crackers with toppings like salt flakes, dried herbs, or sesame seeds.
Bake the crackers in the preheated oven for about 12-15 minutes or until they turn golden. Keep a close eye on them, as they can burn quickly. Once baked, remove the crackers from the oven and let them cool completely on a wire rack. They will become crispier as they cool down.
Store the einkorn sourdough goldfish crackers in an airtight container for up to a week.