One must distinguish between sourdough starter and the bread or other sourdough products we want to make.
I use those clear glass storage containers with a rubber seal and metal flanges. I leave them open by using the metal sealing moving parts to keep the jar open. I put a shower cap on top of the whole thing to keep bugs out and yet allow oxygen to enter my container.
To create a starter all you do is start with equal parts of rye or wheat flower and spring or bottled water. Rye and wheat have more active wild yeast n them, so it is better to start with one or both of them. Stir the mixture, but don't worry about dissolving all the small stuff, as the fermentation process will do that for you.
You need to feed these micro-organisms daily for about a week, so start of with maybe a 1/4 cup of flour and water. Add equal amounts 2 or 3 times a day for the first 5 days or so. When you feed, stir and thus you are also airating the starter.
The starter should start bubbling and expanding within the first few hours, certainly by a day. That is a good sign you have some wild yeast in there. Do not feed it anything other than the flour and water: no sugar, no salt, no dry yeast, no vinegar. Just don't do it. You want a "pure" sourdough starter.
After a week, you can begin using some of your starter to make stuff. Just remember to keep feeding it weekly. Store it in your frig under the shower cap. When you get this far, post again. We can discuss using this wonderful mixture.
Happy cooking, Marty.