How was a late Zhou dui vessel constructed from two bowls?

In the late Zhou dynasty, the dui was a food container constructed from two identical bowls, each supported on three legs, which formed a sphere when placed together.1

These vessels were created using the piece-mold, or sectional-mold, casting process. In this method, artisans first built a clay model of the object, which was then encased in clay molding. This molding was cut into sections and removed to serve as a mold, while the initial model was trimmed to become a core. The mold sections were then reassembled around the core, with metal spacers used to maintain the necessary separation between the two. Molten bronze was poured into the resulting hollow space to form the vessel. Components such as the loop handles, which were typically found on either side of the rim of each bowl, were often cast separately and integrated into the object using a lock-on pour.21