Using a bowl of a stand mixer, measure out the ingredients and mix them using a dough hook attachment. The easiest way to go about it is to mix water and sourdough starter first so that the starter has a chance to disperse in the water. The order of other ingredients is not important. Mix the dough for at least 5 minutes or until you see it becoming smooth and elastic. (If you don't have a stand mixer, just mix the dough in a large mixing bowl and bring it together with your hands. Knead it for at least 5 minutes to help the dough develop strong gluten bonds.)

The dough should be firm and elastic so that a ball forms and it holds the shape quite well.

Cover the dough with something airtight (a lid, a plastic wrap, or a plastic bag).

Let the dough bulk ferment for 6-8 hours at room temperature. This can be an overnight rise if that fits your schedule.

The next day, after the dough has risen for about 75%, it's time to shape the dough. You should be able to shape it on your counter without adding any extra flour.

Divide the dough into 4 equal pieces and shape them into balls. In the center of each ball, make a hole with your thumb and stretch it. Keep in mind that the dough will rise a second time, so make the holes quite big; they will get smaller after the second rise.

Place shaped bagels on a parchment paper (baking sheet) lined tray, cover them with a tea towel, and wait for them to puff up and rise again. They will not double in size this time, but they should become a bit bigger and puffier. At room temperature, this should take about 2 hours.

Boil the bagels in a pot of water. You'll need about 2 quarts (or 2 liters) of water with the addition of baking soda (1 tbsp) and sugar (1 tbsp). Make sure you don't overcrowd your pot, so the bagels have enough space since they are going to expand a bit when hot water hits them.

You'll find different suggestions for how long to boil them, but I found that 1 minute per side works well (and it's easy to remember). The easiest way to get them out of the water is with a slotted spoon.

With the opposite end of a wooden spoon, you can make your holes just a bit bigger if you wish!

Put them on that same parchment paper lined tray again and put them straight into a preheated oven.

Bake bagels for 20 minutes at about 425°F (about 220°C). If your oven is strong, consider lowering the temperature just a bit so the bagels don't get over-baked. The goal is to get them golden brown, not deep brown.

After baking, allow them to cool completely on a wire rack.