If the problem is actually too much speed, the split flaps described may not help very much. The approach speed is determined by the stall speed, and split flaps deflected 80-90degrees won’t reduce the stall speed significantly. Attempting to fly a steep approach with a clean configuration will in fact result in a faster approach. By adding drag you can make a much steeper approach without picking up speed, which will provide easier control on final. This may be what you need rather than a slower approach speed.