Plot resetting is when you find a random plot house. And if you want to control where you want the house or what villager you want, you simply:
1. Start a new save file
2. Go through Rover's and Porter's chat
3. Walk around town to find a plot
4. If you found one and its a villager/house placement you don't want there repeat steps 1 to 3 until you find one you're happy with
5. Then build a house and demolish it.
Pretty much all you gotta do about plot resetting.