ASYMMETRICAL
Off-kilter in the best way. One large square pillow with a smaller, rectangular pillow arranged on one side of the sofa with another large square pillow opposite. Asymmetrical but balanced.
SYMMETRICAL
Here, repeat your pairing of a large square pillow plus a small rectangular or square pillow on both sides. Up the ante by creating a focal point in the middle of your sofa with one pillow floating in the center.
TAILORED
Button things up with two big square pillows in the center of the sofa with a small pillow in front for maximum crispness.