Thanks! That gives me some fresh ideas!
I changed the topsoil for fresh moist but not soggy in my concrete mixing tub today and put big pieces of pine bark and a slab of rotting pine in the tub, to mimic the places I find them under in the spring. I left their little green plastic dish in with the little dish of meal on top, as they seem to favor that as a hide and the meal attracts slugs and sow bugs, which the salamanders like to eat.

When I took this photo one was under the dish and the other two were under the big slab of rotting pine.

Their box tucked behind the ivy on the east side of the cabin. They seem to favor just being under one of the hides, not burrowing any deeper into the 4 inches of soil even though it is not too dry or too wet, so I think they are happy.
I don't expect them to get out of this tub as the lid is heavy, but I do have the occasional skunk or raccoon come on the property and don't want anything getting into the tubs, hence the bungee cord.