Mix a teaspoon of dish soap in a bucket of water. Remove the legs, lid and grill from the mini barbecue. Dip a rag in the soapy water and wash the the inside and outside of the mini barbecue lid, the barbecue bowl and the grill. Using the same mixture, wipe down the planter. Dry everything off with a clean dry towel.
Measure the height of the planter from the inside. Measure the height of the barbecue. Subtract the height of the barbecue from the height of the planter, this number will be referred to as "the difference." Fill the planter with lava rocks 6 inches higher than the difference. Adding 6 inches to the difference will set the fire bowl of the mini barbecue 6 inches above the planter to give you extra room to work with when charbroiling your food. Lava rocks work well for this project because of their high heat tolerance.
Place the mini barbecue on top of the rocks inside the planter. Fill the surrounding area of the barbecue with lava rocks up to the top of the planter. Make sure to pack the rocks tightly around the barbecue fire bowl to better secure the placement. Remove any rocks that may fall from the planter.
Pour sand over the rocks. The tiny grains of sand will fill in the open areas between the rocks and hold the mini barbecue in place. If you like the look of the sand, fill the planter to the top to display the mixture of sand and lava rocks ,or you can fill the planter up to the last 3 inches to keep the sand out of sight.
Pour easy-light charcoal in the fire bowl and light the fire. Throw the grill on the fire bowl and start cooking.