The third step is actually the first step of the block-in, which establishes the areas of light, middle and dark values, creating the pattern of the composition. When I painted the lower portion of the composition, I had to keep in mind that I wanted it to be a dark valued area, but not as dark as my darkest part which is the large rock near the top.
Each area of value has a light, middle and dark value. So, this area had to be darker than the value of the rocks on the left side of the painting because I want those to be a middle value, but not as dark as the darkest value.
When I finished this step, I noticed that the darkest rock had a shape that looked like a submarine stuck in the rocks. Planning is the key to a good painting! So, I added a dark shape behind it to disguise the sub. I will do a bit more in the following steps.