I caulked the base down and paint the block
I think that would look the best in this scenario.
To the op, are you planning on doing a floor coating? If so I would just use the same stuff on the block and caulk the seam as mentioned ^^
I would go this way and you can find this trim in other colors, I have seen Brown, Tan, and Gray.PVC trim boards. You can find them at Home Depot. I believe they come in widths up to 12 inches. More pricey than PT but you won't need to paint it unless you want a color other than white.
You could start with 1x4 pine, and cut it/plane it to desired size, if the ledge is wide enough. Then paint it .
I'm a primitive I suppose, but I used 1x6 Trex boards, screwed to the plate with deck screws. They'll probably still be there when the house is bulldozed. I don't like PT in interior areas where I'm actually spending time.
I can't remember if I trimmed the bottoms square or not...
