This document discusses a new scheme called Flow Slice (FS) for load balancing traffic across multiple paths in multipath switching systems while maintaining packet order within each flow. FS splits each flow into slices at intervals larger than a threshold and balances load at a finer granularity. Analysis of internet traces shows FS achieves near-optimal load balancing with a slicing threshold of 1-4 ms while limiting out-of-order packets to negligible levels with modest hardware complexity. Simulation results validate the theoretical analyses.