How does salt dough work?
What you get is a polymeric (starch) composite, with salt as inorganic filler.

The salt particles give toughness to the resulting composite, while the starch phase, which is just the same as in your bread, minus the unnecessary blowing agent (baking powder, yeast, whatever), connects the particles in an elastic, flexible way. You get a material that is nearly as hard as a piece of rock salt, but much less brittle.

(Elastic here means more elastic than salt. Dry bread is quite flexible, compared to rock salt ;-) .)

See also https://en.wikipedia.org/wiki/Composite_material