Filling the Bags
Each bag was filled slightly more than halfway. He did not pack the concrete tightly or fill the plastic to the zipper. Leaving some empty space allowed the mixture to move when the bag was placed on the ground. He pressed out trapped air, closed the seal, and wiped away any concrete around the opening.
He repeated the process until several heavy, soft packages sat beside the mixing container. They looked more like strange cushions than building materials. If you try something similar, supporting the open bag inside a small bucket can make filling it easier. The bucket holds the plastic upright and reduces the chance of spilling wet concrete across the ground.
The bags were surprisingly manageable because each contained only a limited amount. Instead of dealing with one large, heavy pour, he could move the concrete in smaller portions. This allowed him to work steadily and stop whenever necessary. Some bags received a little more mixture than others, although the differences appeared deliberate. He seemed to want each piece to have its own dimensions rather than creating a row of identical shapes.