This is certainly a labor intensive project so don't feel hesitant to seek the help of professionals.
How to make a gravel bed:
Step 1: Start by defining the shape or outline of the bed by using rope, twine or in this case a garden hose.
Step 2: Cut into the grass on the perimeter of the hose with a spade going about 4 inches into the soil.
Step 3: Remove 4 inches of grass with your spade in the space you have defined as your bed.
Step 4: Apply a good layer of compost or humus/manure mixture to the soil. This is an important step as your bed won't get the natural compost from decaying mulch.
Step 5: Sprinkle the compost or manure with a fine spray of water and allow it to settle and firm. Spread 2-3 inches of gravel over the surface. You want the level of gravel to be below the surface of the surrounding grass to help keep the gravel in its place.
Step 6: Plants can then be planted, but try not to crowd them. You can even place stones or pebbles to enhance the effect.
Design and pictures by Peter and Kathleen McHoy, The Ultimate Garden Planner