The cruciform is one of my favorite compositional designs. Think of a cross that touches all four sides of your paper but is not perfectly uniform - it is skewed so that it touches each side in a slightly different spot. Incorporating a cruciform design in to your composition is a great way to create a strong visual impact!
I began painting Colorado Barn on dry paper using blue over the entire sky area and brushing shades of burnt sienna in the foreground, only touching the edge in one main spot at the bottom. While the sky was wet, I painted in the darker trees and extended my horizon line to emphasis the cruciform design shape.
When I began painting Tropical Bloom I let the paint vignette off the bottom of the paper and then used darks in and around the flower and leaves to create a cruciform design in the background.
You can see these paintings and more in my Etsy Shop