A cave.

After some searching, you find a perfect cave. A pretty small opening, still large enough for your werewolf form to fit through with ease, but not so large that it would be impossible to cover up, and the inside still seems quite sizable. The cave entrance is also mostly hidden from sight, unless you view it from the right angle.

In fact, it might be a bit too perfect.

There's no way there isn't already something living there. A bear or a troll or something. But it IS still a very good place to stay...