A flooring substrate system of polymer, open cell structural panels that may be attached to framing members beneath or placed atop of a waterproof membrane roof or deck structure. The panels are attached by a clip with a mechanical fastener that can be screwed into the lower framing members at a range of angles relative to the plane of the panel while the mechanical fastener and clip remain in complete mating engagement. The panels may also be operationally positioned using a disk that either has a threaded post that is bolted to the panel through a pin block and washer, a fixed pin or a pair of spring arms that lock onto rabbets in the panel's top face.