First, to get the conditions you describe, it would appear that the water would have to be pretty much enclosed, not flowing, to allow the evaporation to lay down the layer of salt.
Is that correct?
Yup. Not always enclosed entirely, but in open ocean you don't get evapourites.
Second, since we are precipitating salt out of the water, the salt layer would seem to be less than whatever the depth of the water was originally.
Is that correct?
Yes for an individual layer, however you can get repeated inundation and evaporation occurring at the same place, so you might end up with a sequence much thicker than the maximum depth of water at any one time.
So based on those two factors, it would seem that several things are needed:
* we need an enclosed body of water, a lake or inland sea.
You can also get salt deposits in:
-Coastal areas that are periodically flooded but are usually separated from the sea.
-areas where groundwater upwells and evaporates.
-semi-enclosed marine basins in arid environments, as in those that are separated from open water by a shallow strait or rock ledge. Water becomes denser as salinity increases so when evapouration occurs, the more saline remaining water sinks and you get a very saline water body trapped behind the barrier that encloses the basin.
So I'd say you need an enclosed or semi-enclosed body of water.
* we need any outflow from the lake to be less than or equal to any inflow.
* the trapped water must stay relatively undisturbed long enough for the water to evaporate.
I'm not 100% sure what you mean here. I'd just say you need losses by evaporation to be equal to or greater than water inputs (as even fresh water will contain some dissolved salts).
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