Settler Built Settlements Mod
MODGive your settlers supplies, and let them build the settlement themselves
Big thanks to Zed140 for letting me use his Living Series- definitely go check out his work (and if you just want totally pre-built settlements without even having to build the supplies to unlock them, then just use his original mods).
The most common cause is Flicker Fixer: which is an old broken mod that you shouldn't use (Grab PRP instead).