Some of us tried making blocks. It's an easy process. They have a simple four part mold. A shovel full of sand cement mix is placed in the bottom of the mold and tamped down with a tool. Next, three cylinders are inserted to form the hollow core.
More mix is added and tamped firmly.
Here is where it gets tricky. If you don't get enough mix into the corners, you get a weak block. A final shovel of mix is tamped firmly and the top smoothed. Then the core pieces are pulled out and the mold removed. The block is then placed in the drying area and the process starts all over.