Here's my working process, which is basically top to bottom, using the patterns of oak trees to establish movement and direction. I love using diagonals.
Stage two, moving down the painting to start to develope the foreground
End of plein air painting session, about 2 and a half hours. My composition is established and most of my thinking is done, I can see it finished in my mind's eye.( that streak of gray on the lower right is from a shadow cast on the paper.) I usually don't add shapes in the studio, just adjust values because I paint the lightest value that I think should work. It is so much easier to make watercolor go darker, than to lighten it.