Is there any way to avoid the mark left by slitting on a clear polyester decal?
The line left by the slitting process is actually a mark left in the adhesive, not on the material itself. However, the adhesive will continue to flow and that line should eventually disappear. The soap and application method is another way to aid the flow of the adhesive to eliminate any slitting marks. The only way to avoid the mark caused by slitting on clear decals is to not slit the decal at all but then you have lost the benefit of a split release liner for easier application.