You have to have your bird in the oven and at least halfway cooked as Mom always baked her stuffing in a separate dish, and you need juices from the bird to moisten the stuffing. Or if you'd rather, make up a cup of chicken or turkey stock to use.
Mom always said one slice of bread (or so) per pound of turkey. Then add sage, parsley, marjoram (if you have it) and thyme from a quarter tsp to a full teaspoon (less if your making a smaller batch, more in a bigger one....now you see what I have to deal with when trying to reproduce Mother's cooking...), a handful of chopped onion, a knob or two of melted butter or margarine, salt and pepper.
Tear the bread up into small pieces, add your spices, butter or margarine and onion and mix well. Add enough of the turkey juices or stock to make the mixture moist but not "wet". Again, here's where experience tells you the difference. I go by the mixture just holding together. Pile the lot into a buttered, ovenproof dish that's large enough so the stuffing isn't tightly packed and cover with foil. Pop into the oven with the bird for the last hour or so of cooking time. But no less than one hour at around 350F.
She wasn't particular if the bread was stale or not. Day old is about what she used. I know some recipes make out that you can't do good stuffing without stale bread, but Mom's turned out great either way.
