This is from the B-707 flight manual. The leading edge flaps are located as follows:

1 set outboard of the outboard engine pylons ( 4 on each wing)

1 set between the pylons ( 2 flaps )

1 set inboard of the inboard pylon ( 2 flaps )

PURPOSE: To increase the lift capability of the wing for takeoff and landing.

Remarks: The leading edge flaps are hinged at the leading edge and are driven forward approx. 100* from the chord line by hyraulic cylinders. There is no intermediate position; they are fully extended or retracted. The leading edge flaps will extend when the outboard trailing edge flaps extend beyond 9-1/2*.