Evidence for asymmetric plate growth, variable crustal thickness, and non-uniform spreading rates is ubiquitous on the seafloor. However, conventional numerical modeling approaches are often incapable of explaining the non-uniform growth of oceanic lithosphere. Noting that plate-boundary forces can dynamically determine plate speed by finding a balance against the resistance to extension at ridge axes, we introduce plate-boundary tractions instead of kinematics to drive plate motions in numerical models for mid-ocean ridges. We construct such models using FLAC, an open-source finite element code for geodynamic simulations. Our preliminary two-dimensional models for slow-spreading ridges have constant tractions on the boundary far from the ridge. Applying periodic variations in thermal states or magmatic accretion rates at the spreading center, we monitor how plate speed, crustal thickness, faulting styles and fault offset change in time. We also compare the model results to the temporal variations found in the bathymetry and seismic reflection data along a 1500 km-long transect across the slow-spreading South Atlantic seafloor, which were acquired in the 2017 CREST (Crustal Reflectivity Experiment Southern Transect) expedition.