Easy recipe for sourdough starter.
I've used this recipe for decades now.
I did make a mistake when I said that the liquid that forms on top of the starter is fine, the book says it is normal but to pour it off. Especially pour it off after it has been in the refrigerator. Usually happens after storage.
Remember to do 'something' to the starter once a week. Either make something and feed the starter. or throw out one cup and feed the starter.
Feed the starter is replacing what you have taken out or keep it fresh.
Most of my recipes call for 1 cup starter. I would take that out of my jar and then put one cup warm water and one cup flour back into the jar and stir. Then let it sit on the counter 30 minutes until it bubbles again and then cover and put back in refrigerator. That is 'feeding the starter'

2 cups warm water
2 1/2 teaspoons active dry yeast
1 tablespoon honey
2 cups unbleached all purpose flour
(this makes 2 cups)

Put water, yeast and honey in a mixing bowl. Let the mixture stand for 10 minutes. Stir until yeast is dissolves. Stir in the flour and beat until smooth.
Cover the bowl with plastic wrap and let stand at room temperature 2 to 5 days, stirring occasionally. The longer the starter stands, the stronger the flavor.
The starter will bubble and a sour smelling liquid may form on top. This is normal for a healthy starter, so simply pour the liquid off and discard.
To store the starter, pour it into a sterilized jar or crock. Cover and refrigerate.
Give it a try, I think you'll be pleased with the results!