Flagstone is characteristically dark in color and flat. Most stone companies cut flagstone to be a few inches thick and roughly square for building projects. When choosing flagstone, it's best to select stones that are the same thickness. All of this guesswork is removed when you make your own flagstone. The best method to achieve a faux flagstone is to cast it in concrete.
To cast your own flagstones, select Quickrete concrete mix. To get your flagstones a uniform size, use a flagstone mold such as the Quickrete Walkmaker form. The characteristic red, brown, grey, blue and black color of the stones can be achieved with liquid cement color. You will also need plastic sheeting for the curing stage of the project.
The Quickrete concrete mix comes pre-mixed so that all you need to do is add water. Add your cement color to the water, and then combine your wet and dry ingredients. Mix the two until they are the consistency of toothpaste. You should prepare your site in advance by excavating the soil and laying down your weed barrier fabric and base of sand before casting the flagstone. Place the form where you wish the flagstone to be set, and fill the individual slots with the wet concrete. Smooth the surface of your paver. If you wish, you can add natural features, such as pressing leaves or carving animal tracks into the surface of the concrete to form fossils. Remove the mold and cover the flagstone with your plastic sheeting to allow the concrete to cure.