there is a 4 inch diamind grinding disc that attaches to a grinder that will flatten the edges between the stones.But you have to use a torch with water on those spots to pop the stone so the surface regains its texture. the disc takes the texture off the stone. This technique is not really for the average homeowner. Cosult a local mason if your really interested. But those small lips between stones really arent thta bad. Mant times the stones are not perfectly flat on top. Some edges dip down while others go up, so when the two meet you get that small irregularity, it really is a tolerable thing. The stones are not tile and not perfect, no matter how proficient the installer is. Hope this info helps. good luck