Bulk graphite was approximated with a 6L thick slab. We used a plane-wave cutoff energy of 600 eV throughout and left at least 20 Å of vacuum space above the 2D sheets in order to model isolated materials. The k-point grid was set to a Γ-centered 12×12×1 Monkhorst-Pack grid. The local density approximation was used to compute the band structures, ionization energies, and hBN band gaps. A correction to the latter quantities was necessary as both of them are underestimated in semi-local DFT. The scissor correction to the band gap and correction to the ionization energy were obtained by recalculating these quantities in the few-layer (≤ 3L) limit of hBN using the HSE06 functional. We found no dependence of either correction on N and therefore assume that it can be applied to all hBN thicknesses.