Each and every litter is whelped in my bedroom. This allows me to keep a close eye on them for any problems. They are supervised 24/7 for the first two weeks.
Once they are 3.5 weeks old, they move into a larger pen in my kitchen. As they get older and more used to using the potty boxes, the pen is gradually expanded and more interactive toys are added.
See below for set-up examples.
This is the initial set up and remains this way for the first 2 weeks. Once they start moving around more freely on their own, half the box is used for pee pads to start the potty training.
By 3.5 weeks, pups are moved to a bigger pen in a busier area of the house. They have access to crates to get used to a "den" like sleeping area, as well as potty boxes and a few new toys.
By 6 weeks they are mostly potty trained, so the pen is at its biggest size. Crate doors are added to begin nighttime training.
Puppies are allowed outside on the deck several times a day to aid in house breaking. They also get full access to my kitchen and livingroom for play times.