Metamaterials are materials that are designed to exhibit properties which are not found in naturally occurring materials. They can be built by assembling multiple unit cells with different material phases (possibly voids) in repeated spatial patterns. This process generates a lattice with translational periodicity. Commonly in the literature, the directions of periodicity that are considered are those corresponding to the Cartesian axes ---which are orthogonal--- leading to rectangular unit cells. Then, boundary value problems are efficiently solved numerically on a single unit cell, accounting for generalized periodicity conditions. The main drawback of such approach is that it is inherently restricted to orthogonal unit cells, and thereby it does not enable the efficient computation of a wide range of architected materials which are periodic in non-orthogonal directions. In this talk, we extend the previous approach to non-orthogonal generalized periodic structures, and apply it to efficiently calculate the behavior of flexoelectric metamaterials with apparent piezoelectricity. In particular, we find the expressions for macroscopic quantities of interest ---such as macroscopic strains, stresses and electric fields--- in metamaterials with oblique unit cells, and characterize their electromechanical responses under macroscopic actions (sensing/actuation) applied along arbitrary directions, regardless of the periodicity directions of the lattice. Finally, we show that macroscopic quantities of interest of flexoelectric metamaterials ---such as their apparent piezoelectricity coefficient under compression--- can be maximized by optimizing both the angle between periodicity directions and the direction of compression.