There are often specific escutcheon plates (that is what you call a plate that would go behind the current pictured trim piece) to match the handles themselves, just for the reason you posted. You could look on the Kohler site for the specific handle that you have to see if there is that optional piece, then google the part # to find it for sale- not sure where you got that one. There may be a generic one that may also fit if not for that specific model. I learned that word- escutcheon - it applies to all the plates in plumbing, like those little flanges at the base of pipes that cover the wall openings around the pipes ;-) Hope that helps.

If you are interested here is a pic of a bathroom we did a in the last project house. Shower pan was 42x30. We had some space to fill so we created a seat. We had the seat made out of Corian. This was one of my favorite bathroom remodels. It was a 1/2 bath before. When our realtor saw it she ooh and aaahed. I said yes, I love it and wished I had one like that in our home. She laughed and said "Barb, I think you know someone who could do that for you!"

Everyone, thanks for the encouraging words. Gigi, you are in luck. I am in Palo Alto. My stone fabricator is in Redwood City. I am out of town this next week but when I get back I will figure out what we are using to create the side tables. Assuming he hasn't already tossed the tv cutout, we will use that and then the entire rest of the slab is yours. If he has tossed the tv cutout already, I may still need a piece of it, but I will get back to you about the rest. It has a crack all the way from top to bottom (why it was so cheap) but its close to the edge where we cut it so depending on how much you need, it may not be a problem. As for the dog, she is very cute and dear to us, but you probably don't want her because she is quite the lemon from a health perspective. Fortunately for her, she hit the doggie lotto when I adopted her from a rescue. Another pic of her snoozing (wearing DH's sunglasses) with her head on my pillow!

Here is my search for cast iron. the Bellwether has a more modern look than the standard fare. https://www.us.kohler.com/us/browse/bathroom-showering-shower-bases/_/N-2d8rZ1z13vg7?Nr=AND%28product.language%3AEnglish%2CP_market%3AKPNASite%29 I have the 5x3' salient center drain pan and I love it. Comes in a lot of colors. I see that the other 5' lengths don't come as wide which is a shame, cause the 36" width is nice.