We can imagine that a lump of wet clay somehow ended up in the fire, dried out, hardened and formed a hollow shape; a shape that could hold things, in a tough material.

我们可以想象一块湿泥巴最后在火上烧制，烘干，变硬，形成一件形状中空的器皿，材料简陋，不过可以盛放东西。