If you are a type of a person being satisfied by easy answers, then the answer to the question in the title is indeed pretty simple. Injections.
But that would be probably too shallow of an answer cos there and big differences in injection types and the Elephone engineers are using the so-called “nano-injection moulding”. That sounds pretty complex and sophisticated, but in general that this technology is used for the creation of both the plastic components and the metal alloy components.
It’s basically a technique, where the specific liquid heated by the induction is injected into somewhat frozen mould and it cools and hardens. Thus creating very precise metal parts and components. This technology has been used also in the process of making the Elephone S3 and the company is admitting very significant rise in the production cost (allegedly up by 500%) of some particular components. But it adds majorly to the general sturdiness, durability and finesse of the device so it’s all worth it.
The Elephone S3 is not going to dazzle too much with its specs, but the design is a completely different animal and we can expect to have quite a looker on our hands with its arrival. In the meantime you can check the aforementioned process documented on the official video.