Supported polycrystalline compacts having improved shear strength, impact, and fracture toughness properties, and methods for making the same under high temperature/high pressure (HT/HP) processing conditions. The method involves a HT/HP apparatus formed of a generally cylindrical reaction cell assembly having an inner chamber of predefined axial and radial extents and containing pressure transmitting medium, and a charge assembly having axial and radial surfaces and formed of at least one sub-assembly comprising a mass of crystalline particles adjacent a metal carbide support layer. The charge assembly is disposed within the chamber of the reaction cell assembly, with the pressure transmitting medium being interposed between the axial and radial surfaces of the charge assembly and the extents of the reaction cell chamber to define an axial pressure transmitting medium thickness, L.sub.h, and a radial pressure transmitting medium thickness, L.sub.r, the ratio of which, L.sub.h /L.sub.r being selected as less than 1. The reaction cell assembly containing the charge assembly then is subjected to HT/HP conditions selected as effective to sinter the crystalline particles into a polycrystalline compact layer and to bond the polycrystalline compact layer at an interface to the metal carbide support layer for forming a metal carbide supported polycrystalline compact. The supported compact is characterized as having an essentially constant or increasing residual compressive stress on the surface of its compact layer as portions of a predefined thickness, W, of its support layer, as measured from the interfaced, are incrementally removed.