Making images go to external sites in Slick carousel
I found the solution. In the Slick settings, I set the Link to the custom text field. For most of the time I've been working on this that field did not show up in the Link dropdown. But suddenly it did.

At first it's misleading because the Views preview shows the original image with the smaller linked image overlaid. However, if you go back to where the block is placed, the images will appear correctly. Whew!