I was asked about two specific greens: the 15th at Rock Creek, and the 1st at Sebonack. [Actually, also the 2nd at Sebonack, but that was really all Brian Schneider's idea -- I just tried to tone it down enough so it would work!] Those are great examples because both greens are very close to the edge of being unfair, and probably over the line for some people.
The 15th at Rock Creek is a very short par-4 playing downhill to a green site that had a high shoulder on the left, and a rock outcropping on the right that would hide some of the right-hand side of the green. Trying to use both features for hole locations meant that there would be a substantial tier from left to right through the middle of the green -- in many cases, that's the real origin of a severe green, when you are trying to incorporate two different elements that it's hard to fit together.
We intended the hole to be driveable some of the time, but the upper-left section was perfectly defended by a slope made for bunkering in front. So, we left an entrance to the left where you could drive the green but you'd have to putt up the slope if the flag was to the left, and we tried to bank up the left half so that a great shot from the tee had a slim chance of holding the green if it landed just in the front. [If not, it's through the green into a deep rear bunker, so it's very risky to try to drive it onto that portion.] As it happened, I played in the Renaissance Cup with an excellent player who tried to pull off that shot with a 4-wood -- I had moved the tees up so people would try it -- and his shot was ALMOST perfect but just leaked off the tier and down into the lower-right portion of the green. Instead of having a putt for eagle, he three-putted for par, and he was pissed -- but it was the same contour which we'd built to try and hold his tee shot on the top slope, that made it difficult for him to lag his first putt close to the hole.
The first green at Sebonack is a different story. We must have built five versions of this green. When I had explored the pros and cons of working alongside Mr. Nicklaus, a friend told me that very often when they did a walk-through, they got upset about the first hole they would look at, and he eventually figured out it was just a tactic to put everyone on the defensive. Well, every time he'd get to Sebonack, we'd start out on the first hole, and every time, the green would suck, no matter which of my guys had tried to build it.
Eventually, we concluded that we had to straighten the hole, because with the cottages to the left and the boundary too close on the right, we couldn't really encourage people to play to either side. Jack was not happy about that at all, and on one visit he said he thought it was going to be a "zero" hole because there was nothing to work with. It was at that point I determined to give the green a try myself. And with "strategy" restricted by the boundary issues on both sides, I tried to come up with a green that was about shotmaking, where a flip wedge from 50 or 100 yards was a potentially dangerous shot and you might want to try something lower to the ground. So, the main part of the green is tucked between a steep ridge in front and the cliff over the back -- where you afraid a conventional approach might hit on the downslope of the ridge and go over and out. And the other most difficult hole location is right in the middle, a shallow plateau where the ridge flattens out into the green, but it's not deep enough that you can be sure of hitting it and holding it. You can play a normal pitch to the back left part of the green, but if you do that you are foregoing any chance of a three, and maybe even risking a three-putt.
All of that may be too severe for some people, but at least Jack doesn't think it's a "zero" hole anymore.
Funnily enough, an old friend of mine in the business came up there just after we'd finished the green, and offered to demo his never computer system that takes in the contours and speed of the green and computes what line you need to make the putt -- the one they use on TV now. His idea was that he could show us what were "fair" hole locations on the greens, where someone could theoretically make a putt from any angle, and he demonstrated the concept by using the first green at Sebonack. And most of the diagram was black -- i.e., unfair -- including that center hole location, because it was impossible to hole a putt from the back right to there. The thing is, I don't think that's unfair at all. To me, it would only be unfair if you couldn't two-putt the hole.