Lava rocks can add a touch of the rustic tropics when you use them to form a border around your flower garden and other areas. If you live in a place where volcanic activity has occurred in the past 500 years or so, you will be able to find all the rocks you want by wandering around your own property and neighboring areas. If you don't live in a volcanically active area, you can purchase lava rocks at special nurseries and rockeries.
Plan your project before you begin. If you don't have an existing flower garden, decide where it will be and measure the dimensions. Also decide if you want large rocks or small rocks or a combination of sizes, and if you want an "entryway" without rocks that will allow access to the area. You might also want to include attractive, large individual rocks inside the garden area that can help to showcase special flowering plants.
Purchase or collect a sufficient number of rocks to encircle your flower garden.
Rake the areas where your rocks will sit to make them level---you'll want the rocks to sit flush with the ground.
Begin stacking rocks, laying down larger ones first if you plan to build a rock wall. If you are making only a single layer of rocks, set your rocks side by side. You might need to dig into the soil a bit to ensure that rocks with pointed edges sit securely without wobbling and creating a hazard.
Place large, attractive rocks inside your garden area to spotlight special plants. You can also use lava rocks to disguise or hide unattractive areas of your garden, such as faucets or water pumps.