Virtual landscapes in digital games have become more expressive and impressive. However, design methodologies that can efficiently implement them have rarely been developed. In real-world landscape architecture, a design methodology called Overlay Design Methodology has been commonly utilized that allows efficient spatial design by computing the hierarchy and the placement of the environmental resources. In this paper, we investigate how to apply Overlay Design Methodology for the creation of virtual environments within digital gaming contexts. Along with the establishment of the design methodology, we measure the effectiveness of the methodology with protocol analysis and survey to 30 game developers. As we observed, the Overlay Design Methodology doubled the collaboration among team members and reduced unnecessary time in the design process by over 98%.