Latex mattresses are made from natural latex, a milky fluid extracted from the sap of rubber trees. They're typically constructed using one of two methods: the Dunlop process or the Talalay process.
In both cases, liquid latex is poured into a mould. In the Dunlop process, it is then baked. This results in a dense foam with a firmer feel to it.
In the Talalay process, meanwhile, the mould is only partially filled. The lid is vacuum-sealed and then the latex is left to expand. Once it's fully expanded, it's then frozen and only then baked. This creates a foam with softer feel. Some latex mattresses are made using a combination of both Dunlop and Talalay processes.
The latex foam is then cut to size and encased in a mattress cover for comfort and protection. A typical latex mattress is made up of multiple layers of latex foam, plus other materials like wool or cotton may also be added to the mix for extra comfort, and often a layer of springs too.