In this stage I've basically started the process of separating the shadow areas from the lit areas. I've done this with a thin wash of "faux umber", a mix of ultramarine, burnt sienna and yellow ochre applied very thinly. After that I put in some of the half tones in the lit areas to help model the form using terra rosa, yellow ochre and viridian, also applied very thinly.
This isn't much of a block-in. I could have rendered the form more fully using a mineral earth like terra rosa or venetian red, but I know that would lead me to a much tighter painting than I'm planning. To keep my painting more painterly I need a looser foundation.