From here you can get an idea how I arrange my flats.

Whenever I create flats for hair coloring, I divide them into different sections, or clumps of hair as I call it.

Again, this is just my technique that I'm used to, if you have one of your own and it works for you, by all means use it.

As this is a hair coloring tutorial, I went ahead adding the base colors for different sections; the skin, eyes, lips, and of course, the hair.

I usually finish adding the highlights and shadows to the face first before I touch the hair, this is to give me a guide where the light is pointing.

I chose to use a very deep red shade to the hair.