Hi Holly, If I am understanding your question correctly I can think of several possible solutions you could try. It would depend on whether the little lines you are seeing are relatively smooth and just on the surface, or if there is a drop off that you can really feel. If your clay has not yet been baked and the lines are very much on the surface and relatively minor you could start with "petting" the slice smooth with a finger several times to re-align mica, ending up going in ONE DIRECTION ONLY as you finish. You can use a smooth tipped rubber glove or not. You could try this either before or after the cane slice was placed on the scrap clay base. I might start the "petting"-finger smoothing before it was on base and finish up the fine tuning after. You could also experiment using a tiny bit of olive oil on a finger to smooth over the line in that one way petting fashion. If petting is not enough, “therapeutic cosmetic work” can happen after the baking.
If the lines are still marring the surface once you bake the piece, sand it by placing your sandpaper on a flat surface and move the pin surface over the sandpaper (sandpaper specs in URL article below). Then buff. Sanding and buffing can make a HUGE difference in how the surface looks! Takes a fair amount of elbow grease if one wants to do it manually (I do). Just in case you are interested in my ideas on sanding-buffing-varnishing, I thought I'd share the following URLS to past PCC posts.
URL to my PCC thread on hand-finishing off pieces (buffing-sanding) without varnishing so they are shiny, (but not as shiny as using a varnish) http://forums.delphiforums.com/polymerclay/messages?msg=64038.1
URL to my PCC thread on varnishing http://forums.delphiforums.com/polymerclay/messages?msg=64052.4
Updated varnishing info: http://www.melobeau.blogspot.com/2014/03/tute-varnishing-polymer-clay-with.html
To eliminate as much drag on your tissue blade as possible and minimize the lines on the cane to begin with, start with a very sharp tissue blade. Clean it frequently with alcohol. Let it dry before you use it.
Anita in AZ