Split folding rear seats
If you have just one child, the center of the rear seat is usually the first choice, provided the carseat fits well in that position. The outboard seats in the rear are also OK. When we had a single carseat in our Saturn SL2, I chose to put it on the passenger side in the rear.
Split folding rear seats are not a problem for carseats, unless specifically mentioned in the owners manual. On the other hand, folding rear armrests may be an issue. Some Evenflo carseats and Ford vehicles should not be placed in front of a folding armrest.