The lamas begin the work by drawing an outline of the mandala on the wooden platform, which requires a large part of the day. The next few days are spent laying the colored sands, which is done by pouring the sand from traditional metal funnels called chak-pur. Each monk holds a chak-pur in one hand, while running a metal rod on its grated surface; the vibration causes the sands to flow like liquid.
Traditionally most sand mandalas are destroyed shortly after their completion. This is done as a metaphor of the impermanence of life. The sands are swept up and placed in an urn; to fulfill the function of healing, half is distributed to the audience at the closing ceremony, while the remainder is carried to a nearby body of water, where it is deposited. The waters then carry the healing blessing to the ocean, and from there it spreads throughout the world for planetary healing.
Mandala Construction Process: http://www.salisbury.edu/culturalaffairs/monks/open.html