I'm glad you got it worked out, Kodi.
I was hesitant to jump into this because, though I occasionally get involved running everything from maintenance to whole builds, there are obviously much more experienced contractors here...
I live in a pretty hilly part of the Earth and in a really hilly part of that part of the Earth. When I build or have a picket fence built here, I insist on a simple way to follow the terrain and keep the pickets off the soil (what little soil we have). I cut a short piece of picket (usually actually a few), about a foot or so. For each picket that is stuck to the stringers, one of those short pieces gets put underneath, facing perpendicular, as a spacer. It sounds onerous but it really doesn't take very long at all to ensure that the pickets are properly spaced above the ground and follow the terrain gradually.
Using that technique, the biggest problem I've had was the guys tilting the pickets as they go. Even though I've insisted on having a quick look at a level every 3-5 pickets, I've still come out with crap that had to be redone because when I wasn't looking, they would ignore the level.
I feel for you. If I hire someone with pride to do something like that, I generally get a really good job. If I don't and I don't monitor constantly, it often costs more...
Tom