Complex 3D-shaped optics are difficult to coat with conventional technologies. In this research, large top-open optical glass cubes with a 100 mm side length were functionalized to simulate large dome-shaped optics. Antireflection coatings for the visible range (420-670 nm) and for a single wavelength (550 nm) were applied by atomic layer deposition simultaneously on two and six demonstrators, respectively. Reflectance measurements on both the inner and outer glass surfaces confirm a conformal AR coating with a residual reflectance significantly below 0.3% for visible wavelengths and 0.2% for single wavelengths on nearly the entire surface of the cubes.