The people back then had the possibility to melt metals, so they could pour it into molds already.
Molds could be made from metals that would melt at a higher temperature and they could also be made out of sand.
For the latter they could have used wood to cut decorative shapes into, press the wood into really dense sand and then pour the molten metal into the imprint that the wood left in the sand.
Also they had hammers, anvils and many other basic tools and they knew how to use it.
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