This is how I tried to speedily age up a wolf for an RP before I knew this site existed and I could speedrun the game.

You can spawn anywhere, but make sure to take territory around the west of McBride Lake as that's where this suggestion takes place. Once you've completed Learning to Hunt, chose a mate, and created your territory, the below can begin.

The fastest way I've found to grow pups on SC is to live almost exclusively on a beaver dam. There's several to choose from. The one I typically choose is near McBride Lake and Slough Creek, as it has several bushes for puppies to hide in while you hunt or when you get attacked and a very close ren site for speedy travels to the next stage of the game.

Once you've traveled from a den and made it to the dam you can sleep 99% of the time, and hunt beavers to feed your pups the rest 1%. Two rendezvous sites are very close; one literally on the other side of a hill and small creek to the north, and another just northwest-ish.

Image below: Me on the beaver dam, and the nearest 4 dens I've been able to find. As pups would need to be carried or let to swim across the river which will be higher from Spring until Summer, it may be safer/easier to choose one on the left side of the river unless you're confident in your ability to safely get the heaviest pup across.