This is different from the problem we confront when creating possessives with compound constructions such as daughter-in-law and friend of mine.
Generally, the apostrophe -s is simply added to the end of the compound structure :
my daughter-in-law's car
a friend of mine's car.
If this sounds clumsy, use the of construction to avoid the apostrophe :
the car of a friend of mine
This is especially useful in pluralized compound structures: the daughters-in-law's car sounds quite strange, but it's correct.
We're better off with the car of the daughters-in-law.
Many writers consider it bad form to use apostrophe -s possessives with pieces of furniture and buildings or inanimate objects in general. Instead of the desk's edge (according to many authorities), we should write the edge of the desk and instead of the hotel's windows we should write the windows of the hotel.
