Synthetic solid state chemistry has increasingly focused on the rational design of target phases using a variety of techniques to avoid thermodynamic minima.  These synthetic strategies have had a synergistic effect on materials property optimization for energy storage materials, optical lens materials, catalysts, magnetic devices, and a myriad of other materials.  We have targeted ternary sulfide and selenide structures for study due to the diversity of known phases, the relative dearth of topochemical experiments that have been performed on these compounds, and the observation that many structures that should exist have not yet been synthesized.  In many of these materials, the structure type is determined by packing factors associated with ion size; ion exchange reactions should result in new structure types.  The layered phase KLaSe₂ rapidly reacts with solid NaI at temperatures < 600 ^oC to form the first reported ordered layered phase of NaLaSe₂ (as opposed to the known disordered rock salt phase) by using the extracted alkali ions to generate a molten eutectic salt in situ.  This technique, driven by metathesis, should allow the fractional substitution of phases that may otherwise prove unreactive towards ion substitution.  X-ray characterization data, results from exchange reactions on related phases, and exfoliation experimental results will be presented.