Firstly, the other courses aren't blocked from stroke play .... they were designed solely as CTTH courses, and I wouldn't expect to see them as anything but that.
To answer you question though, Bethpage easily has more reasonably flat greens than the other courses, especially the front 9.....#2, the back half of #3, #5, #6, #9 .. all good holes to waste a little time doing some putting practice.