Those are not Fowler flaps, they are Slotted flaps.
The Fowler flaps combine very significant aft movement to increase wing area, with downward movement to increase camber.

Since such a mechanism is far more expensive to produce, with a questionable advantage for light aircraft, they are rather non cost effective which is probably the reason we usually see them only on heavy transport aircraft or very specialized STOL aircraft.

I think Robart used to sell a mechanism for making Fowler flaps on models.