Salt flats are flat expanses of ground covered with salt and other minerals. Salar de Uyuni in Bolivia is the world’s largest salt flat. Salt flats are visibly very flat, but like every other geology features, they all follow the curvature of the Earth.
Flat-Earthers take the flatness of Salar de Uyuni and other salt flats as ‘evidence’ of a flat Earth. They are wrong. While most salt flats appear flat, they still gradually curve and follow the curvature of the Earth.