Here are the steps to make a sourdough starter:

Ingredients:

100 g all-purpose flour
100 g water
Instructions:

In a large mixing glass jar or a ceramic container with a lid, combine the flour and water and mix until a thick batter forms.

Cover the jar with a lid or plastic wrap and let it sit in a warm place for 24 hours.
After 24 hours, discard half of the mixture and add in 50 g of all-purpose flour and 50 g of water. Mix until well combined.
Repeat the feeding process (step 3) every 24 hours for the next 5-7 days, or until the mixture is bubbly and has a sour smell.

Once the sourdough starter is active and ready, it can be used to make bread. You can store the starter in the refrigerator and feed it once a week to keep it alive.

Note: The sourdough starter may take longer to become active in some cases, depending on the temperature and humidity of your environment. Be patient and keep feeding it every 24 hours until it’s ready.

Here is a link to the jar I use. I take the rubber ring off the top to let any gas escape. This prevents any build-up in pressure and unwanted explosions!

Kilner Round clip to glass jar