Hi Dannie,
Sure, I can help you with this.
Yes, you're right, the outline is still visible because some of the cane slices were thicker than others. Ideally, the slices should be no thicker than two business cards (.5 mm).
If you're applying the slices over a dry enhancement with a dot of glue, gel, or acrylic, then allow that to dry and then gently file the thicker cane slices until they are more uniform in thickness. But be very careful doing this because you could easily file right through the design. Brush all of the dust away and then add your next layer of gel or acrylic.
Another way is to use a tiny ball of blue poster tack (sticky tack) on the rubber end of a pencil and place your cane slice on it. File the cane slice until it's thinner, then apply to the nail. This is time consuming, so maybe thinning your slices like this is something you'd want to do in front of the tv in the evening. Place the slices back in their baggie or container and then you'll have nice, thin slices to use on your customers the next day.
If you decide to buy canes that aren't pre-sliced, you can avoid some of the thickness issues by slicing REALLY SLOW. You don't want to use a sawing motion, back-and-forth. Just a very slow push with the blade, keeping it horizontal to your cutting surface.
I hope this helps! And I'm glad you like Bonnie's canes. She's a wonder, isn't she!
Cat