Garden Bed Construction with Lumber
Select 2 x 6 or 2 x 12 inch construction grade redwood or cedar lumber boards. Fasten one above the other to 4 x 4 posts to make the bed 12 to 24 inches high and whatever length desired. Use lag screws or brass deck screws 3 1/2 or 4 inches long to secure boards to posts that have been set at least every 4 feet.
Set boxes with their tops level in a shallow trench for more secure positioning. Amend soil as required and fill boxes. Irrigate beds to settle the soil.