The invention concerns a process of preparing a thin layer to be transferred onto a substrate having a surface topology and, therefore, variations in altitude or level, in a direction perpendicular to a plane defined by the thin layer, this process comprising the formation on the thin layer of a layer of adhesive material, the thickness of which enables carrying out a plurality of polishing steps of its surface in order to eliminate any defect or void or almost any defect or void, in preparation for an assembly via a molecular kind of bonding with the substrate.