I have a lot of experience with a very badly designed short game practice area. This was at the golf team facility at the University of Oklahoma.
The problem? The designer forgot that the front, sides, and back of a real green on a real golf course tend to be different. And, importantly, most short game shots are played from the front or sides of the green, and much less frequently from over the back.
The designer at OU tilted the green towards the near edge of the property - so, essentially, the area in "front" of the green was cut off within 5 yards by a berm and the property line. There was no room to play shots from in front of the green, where most short game shots actually occur.
The "back" of the green opened up to the driving range - except that it was higher by about 4 feet, and sloped away, and covered with rough, rendering it mostly blind and nearly useless. There was no place from which to hit realistic shots.
So my advice would be, construct your practice area to replicate real greens and real golf holes. An englarged version of something similar to a green on your course might be a good idea. Keep the front, sides, and back of teh green in perspective.
That will give you the chance to practice shots that you'll actually face on your course or any other golf coruse. After all, that's the whole point, right?