The Slaked Plains are a region of drab salt-flats in that most rugged and individualistic of Discworld lands, The Great Outdoors. The brief description of the location in The Compleat Discworld Atlas states that an extreme sect of Omnians thought odd and schismatic even by the standards of that religion fled here to avoid persecution and now make a living by mining and harvesting the salt.
A Discworld "North America". Salt flats round a salt lake. An odd religious sect who fled to avoid persecution. Hmm. In there, is there a family of musical sons with collective gleamingly perfect teeth? Is their oddly localised form of Omnianism re-exported to the rest of the Disc via persistent missionaries with Great Outdoorsian accents?