The sand casting process is also known as "lost wax casting". A model of the item to be cast is created in wax and attached to a "tree" that will include a funnel section for pouring. The model/tree is then dipped in a sand coating until a shell is formed. If I remember correctly from my days working in a foundry, it is about six coats. The wax is then melted out leaving the mold. The metal is poured into the mold and allowed to harden. Once cool the mold is broken and the part(s) are cut free of the tree and the nub is ground off. It's a long, hot and sometimes dangerous process.
John