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.
When gardening in these beds only means you are growing your flowers and vegetables above the ground. You can create your own by building a wooden structure with drainage holes in the bottom and fill it with your favorite organic soil mixture. Concrete blocks, bricks, or just about any material strong enough to hold the garden bed and raise it above the ground can be used.
Circular raised beds with a path to the center (a slice of the circle cut out) are called keyhole gardens. Often the center has a chimney of sorts built with sticks and then lined with feedbags or grasses that allows water placed at the center to flow out into the soil and reach the plants roots.
Vegetable garden bed construction materials should be chosen carefully. Some concerns exist regarding the use of pressure-treated timber. Pine that was treated using chromated copper arsenate or CCA, a toxic chemical mix for preserving timber that may leach chemicals into the soil which in turn can be drawn up into the plants, is a concern for vegetable growers, where part or all of the plant is eaten. If using timber to raise the garden bed, ensure that it is an untreated hardwood to prevent the risk of chemicals leaching into the soil. A common approach is to use timber sleepers joined with steel rods to hold them together.