Pour some dry Aragocrete Gravel around this leg so that it does not slump. Repeat this process to create the other two legs. Carefully use one of your sticks to make a hole in the top of the table. As soon as you have formed this hole pour dry sand into it to keep it from slumping closed. Cover the entire sculpture with more gravel and wait 24 hours before you uncover it.
Arches make great places to attach sps corals.
Arches can be made very thin and tall and because of their open shape they allowed great water flow. Starting in the bottom corner of your Styrofoam box scrape out an arch shaped depression in the sand that ends in the other bottom corner. Add enough Aragocrete mix to slightly over fill this depression. Using one of your sticks make several small holes through the Aragocrete. Fill these holes with dry sand.