Each Soleri Special Assembly is unique with hand carved Styrofoam Sculptures made by Paolo Soleri himself. Paolo uses a "lost styrofoam" casting technique in foundry sand. Special Assemblies are casted at both the Arcosanti Foundry and Cosanti Foundry.

At Arcosanti, Cliff Hersted is seen here carefully laying out each sculpture. Pieces must be laid to use the space as efficiently as possible while still leaving enough space for the foundry sand to hold back the molten bronze. The mold is made with 2 halves, initially separated by a piece of plywood.

This half will become the bottom of the mold.

After the styrofoam pieces are placed. Sand is hand packed around each piece to preserve the detail of the original.