In this paper, we design, fabricate, and test an FSS based on a patch antenna/microstrip-phased array to create a surface with angularly dependent thermal emission/absorption. The structure supports guided leaky-wave-type modes with forward and backward propagating branches coupled to transverse magnetic (TM)-polarized radiation. The choice of microstrip transmission lines leads to significantly better propagation lengths, and hence increased angular selectivity compared with previous coplanar strip designs. Because of metal losses at IR wavelengths, there is a distributed load throughout the FSS which differs from conventional RF design. However, after optimization, we are able to demonstrate a structure with high absorptance. These experimental results show reasonable spectral/directional agreement with the simulation. This work differs from previous reports because the thermal energy couples to the resonant patches and propagates along guided modes as opposed to via surface waves. In other words, it combines the functions of a leaky-wave antenna and a series array. The ability to achieve an angular response including near-unity absorption over a compact area may be useful for future sensors and emitters. This paper presents the design and fabrication procedures along with experimental results for the device.