The full scale Storch was equipped with slotted flaps, which work alike any type of flaps, only that the provide a higher coefficient of lift to a wing.
In simpler words, they are more effective or powerful for relative same area of flaps.

Copied from: http://en.wikipedia.org/wiki/Flap_(aircraft)

"Slotted flap: a slot (or gap) between the flap and the wing enables high pressure air from below the wing to re-energize the boundary layer over the flap. This helps the airflow to stay attached to the flap, delaying the stall."

Copied from: http://en.wikipedia.org/wiki/Fieseler_Fi_156

"Design and development
In 1935, the RLM (Reichsluftfahrtministerium, Reich Aviation Ministry) put out a tender for a new Luftwaffe aircraft suitable for liaison, army co-operation (today called Forward Air Control), and medical evacuation, to several companies. Conceived by chief designer Reinhold Mewes and technical director Erich Bachem, Fieseler's entry was by far the most advanced in terms of STOL (Short Take Off and Landing) performance. A fixed slat ran along the entire leading edge of the long wings, while the entire trailing edge, inspired by earlier 1930s Junkers "double-wing" aircraft wing control surface designs, including the ailerons, was a hinged and slotted flap."