Would like to have your recomendations. -Need to put in edging around a new yard. Single row, with landscape rock behind it. -Edging material is concrete edging "bricks" (the kind you can buy at many places, bull nose interlock with next. Have seen instructions that say to just dig trench, put up a line for straigtness & height, and set away, using dirt, sand to level. Is this correct? Do you need to overexcacate, fill with sand, compact? Probably a simple matter to you pro's, but ..... Thanks!