We report a large-area broadband optical absorber consisting of Ag/SiO2 stacked plasmonic layers fabricated on a self-assembly polystyrene sphere monolayer using the glancing angle deposition. Such an absorber can absorb more than 90% of light in the spectral range of 350 - 850 nm when the polystyrene spheres have a diameter of 750 nm. The broadband absorption is due to the overlap of localized plasmonic resonance wavelengths resulting from different patchy sizes and shapes of Ag coating on polystyrene spheres. Such a simple, flexible and large-area absorber has potential applications in light cloaking and energy conversion.