An inverse-trapezoidal micropattern (ITM) has been considered as an optimal light outcoupler for a light-guide plate (LGP) in display devices thanks to its superiority in re-directing the light to the vertical direction. However, the ITM is not suitable for mass-production because of its over-hanging shape. Therefore, mass-production of the LGP having ITMs still remains challenging and has not been demonstrated before. In this paper, we propose and demonstrate a new structural design and mass-producible fabrication method for the I.GP having ITMs as a light out-coupler. Whereas the conventional method directly fabricates the ITM using soft molds, an approach which is not mass-producible, the proposed method reverses the idea. We first fabricate trapezoidal micropattern using a rigid metallic mold and then bond it to the flat LGP substrate without optical glue. Using the proposed method, we fabricated a slim (similar to 0.6mm) 5.5 inch LGP having ITMs and confirmed that there was no difference in optical performance between LGPs fabricated by the proposed mass-producible method and the previous soft-molding method. This method can be a model approach for mass-producing other overhang-shaped micropatterns as well.