We present an algorithm which we use to identify easy subproblems for packing problems. The algorithm is polynomial in the number of bins and item types and is based on a flow computation in a bipartite compat- ibility graph. It outputs the largest subproblem satisfying the dominance criterion and a feasible solution to this subproblem. The algorithm is well suited to be integrated in a branch-and-bound solver for packing problems and can be adapted to work on many problems, including single or multi-dimensionnal bin packing, vector packing, cutting stock, packing with conflicts, etc.