Draw the outline of your flower bed on the grass with spray paint. Remove the grass within this outline by either digging it out with a flat-edged shovel or spraying herbicide on it.
Hammer a stake into the garden bed's highest end until the top is flush with the soil's surface. Move 1 to 2 feet over and begin hammering in another stake. Place a level on top of the first stake. Hold the level straight. Hammer the second stake in until the level rests on its top and shows the two stake tops are level.
Move another 1 to 2 feet down and hammer in a third stake. Use the level to position the stakes' tops at the same height. Continue until there are stakes across the entire length of the flower bed. If your flower bed is wide, work your way across its width using this technique.
Lay garden edging around the flower bed. Use bricks, stones or timbers. To hold the edging firmly in place, dig a 1- to 2-inch deep trench around the flower bed with a shovel. Make the trench as wide as the edging you are using. Place the edging in the trench. If the flower bed is on sloped ground, dig a deeper trench toward the bottom of the hill. Use stackable bricks or stones to build up the lower end of the flower bed, making it flat and level across the top surface. The height of the edging should match that of the stakes around the bed.
Pour topsoil into the garden bed. Smooth the topsoil with a garden rake so that the surface is level with the tops of the stakes. Either remove the stakes or hammer them further into the ground so they are not visible.