“The Technique of Bronze Statuary in Ancient Greece“, an essay from the Met, describes how the ancient Greeks created bronze statuary.
The earliest large-scale Greek bronze statues had very simple forms dictated by their technique of manufacture, known as sphyrelaton (literally, “hammer-driven”), in which parts of the statue are made separately of hammered sheets of metal and attached one to another with rivets. Frequently, these metal sheets were embellished by hammering the bronze over wooden forms in order to produce reliefs, or by incising designs using a technique called tracing.