Off-axis projection is a common practice for reconstructions of Fourier holograms displayed on liquid crystal on silicon (LCoS) spatial light modulators (SLMs), as it spatially separates the image from the undiffracted light. Binary gratings encoded within the holograms enable maximum angular separation. However, as a result, two mirror images of equal intensities are present in the reconstruction. To introduce asymmetry to the intensity distribution and suppress one of those images, we propose a phase mask with a subpixel pattern. Presented results prove the potential of in-built SLM phase-mask layers for optimizing efficiency of the off-axis holographic projection.