Laser-based powder bed fusion (PBF-LB) involves highly coupled multiphysical phenomena, including melting and solidification, phase changes, evaporation, buoyancy-driven flow, surface-tension effects, and microstructural evolution. Spatio-temporal beam shaping techniques - based on spatial and temporal modulation of the laser beam - enable redistribution of laser energy, mitigation of local overheating, and improvement in print quality. In this work, a multiphysics computational fluid dynamics (CFD) model is developed using the open-source code OpenFOAM to investigate the spatio-temporal beam shaping in PBF-LB of 316L stainless steel (316L SS). The temporal modulation model is validated against in-house experimental measurements and reference data [1] through comparison of melt-pool cross-section profiles. The spatial beam shaping implementation has been previously validated for copper in [2] and is directly applied here to 316L SS. Both continuous and pulsed laser modes are examined for several regular beam profiles to assess their effects on melt-pool behavior. Results demonstrate that spatial beam shaping using a ring-shaped beam profile significantly reduces excessive central melting and suppresses keyhole formation compared with a conventional Gaussian beam profile. Triggering temporal beam shaping leads to fish-scale surface patterns, observed both numerically and experimentally, arising from the partial overlap of discrete melt pools under pulsed laser operation. Furthermore, the transient melt-pool volume and geometric dimensions are quantified to analyze melt-pool dynamics under pulsed lasers with varying frequencies and duty cycles. The results provide fundamental insights into the effects of process parameters on melt-pool behavior when spatio-temporal beam shaping is employed. References \bibitem{Paper} C. Kamath, B. El-dasher, G. F. Gallegos, W. E. King, A. Sisto, \emph{Density of additively-manufactured, 316L SS parts using laser powder-bed fusion at powers up to 400 W}, The International Journal of Advanced Manufacturing Technology, Vol. 74, pp. 65-78, 2014. \bibitem{book} B. Zhou, J. Barode, V. K. Nadimpalli, A. Bauch, D. Herzog, J. H. Hattel, M. Bayat, \emph{Multiphysics simulation of spatial-temporal beam shaping in laser powder bed fusion using OpenFoam}, Proceedings of 14th International Seminar "Numerical Analysis of Weldability", pp. 16, 21-24 September 2025.