Another picture of the monks working; the monk closest to the camera is incising a design into a background using a stylus (the point of a compass, actually); the monk at rear is adding a line of sand to the incised design:
At the end of the day today, the mandala was nearly complete:
It is hard to see in this photo, but the mandala is not a two-dimensional work; the sand is built up in low relief that is difficult to capture in a photograph.