This letter addresses the synthesis of reflective cells approaching a given desired Floquet's scattering matrix. This work is motivated by the need to obtain much finer control of reflective metasurfaces by controlling not only their copolarized reflection, but also their cross-coupling behavior. The demonstrated capability will enable more powerful design approaches-involving all field components in phase and magnitude-and consequently better performance in applications involving reflective metasurfaces. We first expose some fundamental theoretical constraints on the cell scattering parameters. Then, a successful procedure for controlling all four scattering parameters by applying parallelogram and trapezoid transformations to square patches is presented, considering both normal and oblique incidence.