Polycrystalline ultra-hard constructions are made by subjecting a sintered ultra-hard body, substantially free of a sintering catalyst material, to a further HPHT process. The process is controlled to initially melt and infiltrating a filler material into the sintered ultra-hard body to form a filler region having interstitial regions filled with the filler material. The filler region extends a partial depth into the sintered ultra-hard body and is formed at a temperature below the melting temperature of an infiltrant material. Next, the process is controlled to melt and infiltrate the infiltrant material into the sintered ultra-hard body to form an infiltrant region that extends a partial depth into the sintered ultra-hard body. A portion of the filler region and/or the infiltrant region may be removed to form a thermally stable region.