The Pascal Flats are shown on Ben's map when he and Alex are traveling to the radio tower. ("Through the Looking Glass, Part 2") Not much is known of this area other than it is south of the Barracks and the Pearl, and southwest of the radio tower. Ben and Alex travel from the Pascal Flats to intercept Jack and the survivors heading to the radio tower, while the rest of the Others head from there to the Temple. ("Through the Looking Glass, Part 2")
This could be an homage to the 17th century scientist Blaise Pascal who in 1654, was profoundly affected by a mystical experience and abandoned science for theology.