One of the more effective tools for studying low-energy nucleon-nucleus scattering has been the Multi-Channel Algebraic Scattering (MCAS) method, which solves the coupled Lippmann-Schwinger equations in momentum space. A key aspect of the MCAS approach has been the consistent description of both bound (sub-threshold) and scattering states of the compound system, with a proper handling of the Pauli Principle. This talk will present the fundamental aspects of MCAS, at a conceptual as well as mathematical level,with application to low-energy nucleon-nucleus scattering, especially those cases leading to compound states of exotic nuclei.