Passive-tension flap closure of primary wounds remains the most important factor for achieving predictable bone augmentation outcomes. So far, no specific surgical technique has been proposed for major flap advancement, specifically in the thin tissue phenotype (≤ 1.5 mm thick). This article illustrates a detailed description of the Mucosal Detachment Technique (MDT), which separates the mucosal tissue from the underneath periosteum and aims to achieve adequate flap flexibility to cover high-volume augmentation in the thin tissue phenotype. Separating the mucosa from the periosteum allows maintenance of vascularization and an even distribution of tension among the advanced flap. The MDT allows bone augmentation procedures in thin tissue phenotype flap. The flap advancement permits tension-free primary closure in all tissue phenotypes (both thin and thick), independent of the degree of volume augmentation.