In a mixing bowl, combine the bread flour, active sourdough starter, and water. Mix until a shaggy dough forms.
Add the sea salt and knead the dough for about 10 minutes until it becomes smooth and elastic.
Cover the bowl with a damp cloth and let the dough rest for 4-6 hours at room temperature until it doubles in size.
Once the dough has risen, gently deflate it and divide it into 8 equal pieces (about 110g each).
Shape each piece into a ball, then use your finger to pierce a hole through the center to create the bagel shape.
Place the shaped bagels on a parchment-lined baking sheet and cover them with a damp cloth. Let them rest for about 30 minutes.
Bring a large pot of water to a gentle boil and add the malt syrup or honey.
Carefully place the bagels into the boiling water, cooking for about 1 minute on each side.
Remove the bagels with a slotted spoon and place them back on the baking sheet. If desired, sprinkle toppings onto the wet bagels.
Preheat your oven to 425°F (220°C).
Bake the bagels in the preheated oven for about 20 minutes, or until they are golden brown.
Allow the bagels to cool on a wire rack before serving.