If the earth stopped rotating that would cause the sun and moon to appear to be frozen in the sky.
The moon would have to stop too.
And the earth would have to change to a rotation that matches it's yearly orbit in order to keep facing the sun with the same side - like the moon does. B/c it rotates and revolves
But something completely unexpected may have happened too, involving time dilating effects. Whatever He did, it was something only God can do, as the sign to Hezekiah