Green leaf lettuce and other loose-leaf varieties can be planted fairly close together, which make them ideal for containers. A decent harvest can be expected from a medium sized pot. You can 3x the lettuce using a Little Crop Circle.
Growing lettuce plants in a circle provides more space for leaf development, particualrily larger head lettuces like iceberg, romaine and butter. In the garden, sow seeds or plant transplants in a circular row spaced evenly around the perimeter of the Little Crop Circle. Romaine lettuce can be planted closer together than head lettuce. A second row of lettuce plants can be planted around the first row. Ideally, different types of lettuce are grown in each row; leaf lettuce in the first and romaine in the second for example.