Fallout 4 - Building a fence on a slope. Here is one work around to building your fence on a slope and get it to look half-way decent. In the console after selecting the fence piece, use the command 'modpos'.
Example: modpos z -10
number = [positive or negative number for up or down positioning]
Tags: Fallout 4 - Building a fence on a slope, Fallout 4, Fence