A salt flat is what remains when a lake has gone, so dream tradition links it to emptiness after strong feeling. Its blinding white expanse is also read as clarity with nothing left to hide behind.
Has this come up in your dreams before? What was going on in your life then?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.