Take a large piece of paper and coil it around the plants like a funnel. Place a piece of tape on the paper to keep it tight, and away from the edges of the vessel. Begin to pour the sand inside the vessel; pour one color on one side, then try alternating colors. (Note: Leaving the sand to pour in one spot for a period of time will create a little mound. Pour an alternating color of sand next to it to achieve variegated layers.) Step back periodically to look at the progress, adding more sand on the sides to make it somewhat level. Once you've filled up your container as much as you like, pull the paper out, exposing the plants. The sand will fill in around the pots nicely, holding them all in place.