1. Combine Wet Ingredients and Yeast: In a large mixing bowl, whisk together the warm water, sourdough discard, granulated sugar, and instant yeast. Let this mixture sit for about 5 minutes until it looks slightly foamy, indicating the yeast is active.

2. Mix the Dough: Add the all-purpose flour and salt to the wet mixture. Stir with a wooden spoon or your hands until a shaggy dough forms. Turn the dough out onto a lightly floured surface and knead for 8-10 minutes until it becomes smooth and elastic. It should spring back slightly when poked.

3. First Rise (Bulk Fermentation): Place the kneaded dough in a lightly oiled bowl, turning it once to coat. Cover the bowl with plastic wrap or a clean kitchen towel and let it rise in a warm place for 1.5 to 3 hours, or until it has nearly doubled in size. The exact time will depend on the temperature of your kitchen.

4. Shape the Bagels: Gently punch down the risen dough and divide it into 8-10 equal pieces. Roll each piece into a smooth ball. To form the bagel shape, poke a hole in the center of each ball with your thumb and gently stretch the dough to create a 1-inch hole. Place the shaped bagels on a parchment-lined baking sheet, leaving some space between them.

5. Second Rise (Proofing): Cover the shaped bagels loosely with plastic wrap or a kitchen towel and let them proof at room temperature for another 30-60 minutes. They should look slightly puffy. While they are proofing, preheat your oven to 425 F (220 C) and bring a large pot of water to a rolling boil. Add the baking soda to the boiling water.

6. Boil and Top: Carefully drop 2-3 bagels into the boiling water at a time. Boil for 30 seconds to 1 minute per side. This boiling step is crucial for creating the chewy crust. Use a slotted spoon to remove the boiled bagels and place them back on the parchment-lined baking sheet. If desired, sprinkle with your chosen toppings immediately after boiling.

7. Bake to Golden Perfection: Bake the bagels in the preheated oven for 18-22 minutes, or until they are golden brown and cooked through. The exact baking time may vary based on your oven.

8. Cool and Enjoy: Transfer the baked bagels to a wire rack to cool completely before slicing and serving. This allows the internal structure to set properly.