A flexible circuit is populated with integrated circuits. Integrated circuits populated on the side of the flexible circuit closest to the substrate are disposed, at least partially, in what are, in a preferred embodiment, windows, pockets, or cutaway areas in the substrate. In a preferred embodiment, the overall module profile does not, consequently, include the thickness of the substrate. Other embodiments may only populate one side of the flexible circuit or may only remove enough substrate material to reduce but not eliminate the entire substrate contribution to overall profile. The flex circuit may be aligned using tooling holes in the flex circuit and substrate. The flexible circuit may exhibit one or two or more conductive layers, and may have changes in the layered structure or have split layers. Other embodiments may stagger or offset the ICs.