We present preliminary results from an experimental study of optically-assisted assembly. Interference patterns, formed by the intersection of two coherent laser beams, result in periodic one-dimensional potential wells ("optical trenches"). Polystyrene spheres become trapped in these potential wells and subsequently self-assemble into a two-dimensional periodic structure. The spacing between optical trenches is adjusted dynamically, which offers the freedom to dynamically control the lattice constant, offering a recipe for defect-free assembly which begins with annealing at large lattice constant and subsequent compression into a close-packed structure.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.