Example from BAe146 et al.
Large, almost full span, split (slotted) fowler, and tabbed, trailing edge flaps chosen for very high lift – role of the aircraft.
Use of leading edge devices was avoided due to the additional complexity / weight, but mainly as they are often associated with large trim changes, which may have required a trimming tailplane and / or powered elevator; thus avoiding more complexity and weight on what was to be a manual control aircraft.