Urban gardening is now very popular these days because of food safety awareness, our financial economy, and because we want to be eco-friendly. Just because you only have a garden area that is very small does not mean you cannot use some small raised garden beds on a patio, deck, or back porch for some herbs, vegetables, flowers, or ornamental plants to enjoy.
Another approach is to use concrete blocks, although less aesthetically pleasing, they are inexpensive to source and easy to use. On the market are also prefab raised garden bed solutions which are made from long lasting polyethylene that is UV stabilized and food grade so it will not leach undesirable chemicals into the soil or deteriorate in the elements.
This also makes more space available for intensive crop production. They can be created over large areas with the use of several commonly available tractor-drawn implements and efficiently maintained, planted and harvested using hand tools. This form of gardening is compatible with square foot gardening and companion planting.
Lastly, connect your anchors using a heavy-duty string or twine, creating a grid-like pattern of planting squares. You can see an example of the results of this process in my garden bed here: Square Foot Planting Squares.