Answer: A raised bed can be built as simply or as elaborately as you wish. You could just rake soil mixed with amendments such as compost into a flat topped raised area and leave the sides natural. You could use stones, bricks, cinder blocks or lumber or any locally available material for the sides. You could also use the "boards" made from recycled plastic that is longer lasting than wood would be when used in contact with the ground.
Note that the raised bed does not have a bottom; the native soil below should be loosened and mixed in with the soil for the raised bed. Your local county extension should be able to help you determine the most appropriate soil mix for the bed as this would depend on the native soil as well as what plants you intend to grow in the bed.
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