In the last few years, the study and interest on metamaterials has increase significantly, including a keen focus on their manufacturing. In our work we present a way to harness the well-known Rayleigh-Plateau instability of multiple fluid threads placed within a curing elastomer solution to rapidly manufacture elastic mechanical metamaterials. This method allows the positioning of spherical inclusions of a fluid periodically within an elastic matrix and, thereby, control the dispersion of elastic waves in a periodic medium by only changing a small set of control parameters.