Choose the place for the island. Opt for an area that you can see from various angles around your house; alternatively, use a portion of your lawn to which you want to draw viewers or that you want to conceal.
Lay out a rope or hose around the area in the shape you want; adjust the shape until it pleases you. An "island" does not have to be a perfect circle.
Use spray paint to mark the perimeter after you have decided on a shape.
Remove the grass from the inside of the island. Dig deep enough to get all the roots and leave a clear surface for new plants to grow.
Line the outside edge of the island with rocks or bricks. If you want to create an edge for easy mowing, dig deeply enough that you can place the bricks level with the ground.
Fill the island with topsoil, using a rake to distribute it smoothly.
Add the desired plants. For most flowers, small plants and other grasses, dig down about 6 inches to plant them. Trees and shrubs require a hole as deep as their root balls.