Really depends upon ones definition of FLAT. 1st off, anything less than 2% won't drain. Jeff likes 2-5% but at 5%, that's 5' verticle in 100' or 15' in 100 yds. Not very flat in my book. I would offer that Flat is <2%. Flat is when you don't see anything dug below the groundline and anything above it blocks the view of the ground behind.
Drainage become paramont in flat land design. The soil type is also a big determinant as to how you plan your concepts. If you have a sandy soil or are blessed with deep topsoil, you can create a lot of rolls and valley swales to move water without having to strip the entire area (but drainage inlets will be needed to pick up that water).
If the topsoil is thin and must be salvaged for any grading, there are several options.
1) cut a swale down the inside of the hole and use the cut dirt to raise the outside of the hole. slice several swales across the fairway and use that dirt to elevate the areas in between.
2) keep green "at grade" knowing that greensmix and gravel will raise it 1' and cut out around the green, pushing that soil away from the green. Also depress the approach to a swale about 30 yards from the green. Push this material back into the fairway to create enough movement for drainage/interest. For Bunkers, these are really tricky. The best way is to start cutting about 100' back along the line of site. Push this cut material to the beyond the rear of the bunker to raise the backing several feet. The end result will be a bunker 2' deep bunker that a) you can see and b) appears to be 3-4' deep. A low basin in fornt of the bunker will pick up water before it reaches the bunker and allow more vison. The leading sand edge is only 6-8" deep. These work especially good at being gathering bunkers while providing a kick-slope if one carries it so having them more internal to the fairway rather than along the sides works to add strategy. Having them cut into the ground without shape backing mounding makes them appear more natural.
Cut the area between the tees and fairway to generate material to elveate the tees a bit. You can also swale the non-access site to make the tees appear more elevated.
Like Jeff allluded to, all this has to be tied back into an existing grade at some point so the gentler and broader you can be with your slopes, the more natural it will appear. However, you may wish to do some "out-in-rough" grading along the same line to make it looks more cohesive. One problem I see is when archies only grade the play areas and the terrain becomes disjointed or when greens, tees, bunkers and mounds are all built above the grade while everything else is pancake flat. I call this the 'ice cream scooper' look.
BTW, I did template #10 WFW, great hole. And Pat Mucci, you and my father think alike when it comes to Dick Wilson.