Starting out with a base game save file and enabling packs later will allow manual lot placement

If you enable a lot of packs, then the lots associated with certain packs will get automatically placed into the world or save file. This can be very annoying, because the auto placement of lots means you have to do a lot of fixing later. Sometimes, the lots will be placed in a weird direction, where the sidewalk of the lot is not align to the street. So, if you want to place lots yourself, then it is best to start off with the base game save file. Once the save file is created, you exit the game and enable the packs you want. You go back into the game and manually place the expansion pack-associated lots however you want.