Nowadays, the ultimate goal of microsurgical breast reconstruction is not merely the effective transfer of vascularized tissue but the achievement of a natural, symmetric appearance. The aim of this present study was to systematically summarize the published evidence on abdominal-based free flap inset for breast reconstruction in order to provide principles and classification that could guide the surgeon in choosing the most appropriate inset technique based on patient and flap characteristics. A comprehensive review was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, looking for articles on the insetting technique for free flap breast reconstruction. After screening 306 publications, 24 papers (published from 1994 to 2020) were included in the study. We identified four main breast anatomical features on which the papers reviewed focused when describing their insetting technique: breast width, breast ptosis, breast projection, and upper pole fullness. Patient body type, type of mastectomy, and reported complications are also discussed. Flap shaping and inset during breast reconstruction are fundamental steps in any reconstructive procedure. Despite the low evidence in the current literature, this systematic review provides a framework to guide the surgeon's decision-making and optimize the aesthetic outcomes of abdominal-based free flap breast reconstruction.