Measure a square or rectangular area where you want the bed to be built. Hammer a stake or pointed stick in at each of the four corners. Stretch a string between the posts, around the perimeter of the bed. Place a level on the string segments and position the strings so they are level.
Dig a trench just slightly wider than a brick 3 inches below the top of the lawn starting next to the lowest corner. Measure the distance from the string to the bottom of the trench and continue digging the trench, stopping to measure the distance. You want the distance from the string to the bottom to stay the same. This ensures that the first course of bricks will be level. This is especially important on a sloping lawn. Continue until the entire perimeter has a trench prepared.
Lay an inch of sand in the bottom of the trench. Place bricks end to end in the trench to complete the first course of the perimeter wall.
Lay a bead of masonry adhesive onto the top of the first course of bricks and place the second course onto the first, Offset the bricks by half a brick length for a more solid bond.
Continue laying courses of bricks until the wall reaches a height of 12 inches above the highest area of the lawn.