So can you really make bread with only flour and water? The answer is yes, if you have the right flour and the right water.
When I tell people they can make bread with only flour and water, they normally respond that you can't make a true bread without yeast. Well, that is true. But good, raw organic flour will already have yeast on it. Yeast are naturally drawn to things like wheat, grapes, hops and barley. They happily live on the surface of these items until they are destroyed by heat or pesticides. Bread, wine and beer are the result of this long standing attraction in nature. So when I say you need the right flour, I mean flour that is untouched by bleach, heat or pesticides. Most organic whole wheat flours fit this bill, so that's what I use to make my flour and water bread.
So what kind of water is the right kind? You'll need water that is chlorine free (or close to it) and fluoride free (or close to it.) Both of those substances that are commonly added to water are harmful to living beings, and yeast are no exception. So you will likely need to filter your water to make old-fashioned fermented bread with it.
The process is simple but takes time and planning. Luckily, very little of that time requires your participation. I like to keep a batch of bread "starter" on hand at all times, so let's address how to do that before moving on to the actual bread.
Now I must warn those that need exact, precise measurements: you won't find them here. I make bread the way people have for thousands of years, long before standard measuring cups and spoons existed.
You need a clean mixing bowl. How big it is depends on how much starter you want to keep on hand. Use a bowl you won't miss if it's not around for long periods of time.
You want to fill that bowl with approximately one part organic whole wheat flour and two parts water. It doesn't have to be exact. Stir very well and cover tightly with plastic wrap, to avoid introducing any undesirable living things to the mix. Put the covered bowl into a cool (but not cold,) dark place. I use my kitchen cabinets. Leave it there for 6 days. After that, it should have some bubbles in it and an attractive sour smell, similar to wine. If not, leave it until it does, checking every day. This is your starter. It is now ready to be moved to refrigeration.
When you are ready to make bread, stir the starter. Put some of it into a mixing bowl and add salted whole wheat flour until it is the consistency of bread dough. Knead well, then shape into the desired shape. Let rise in a cool dark place for 12 to 24 hours. Bake.
To feed your starter (which should be done about once a week) stir it well. Add water and stir again. Then add more whole wheat flour and stir. Return to the refridgerator. Always keep the water/flour ratio to around 2/1.
Once a week, you will want to add a little bit of water and flour to the starter and stir. Use the same approximate 2 to 1 ratio. This means you will need to make bread on a semi-regular basis. Otherwise you will soon have a whole lot of starter.