Heat butter over medium heat until melted. Stir in poultry seasoning, black pepper and salt to taste. Add celery & onions and cook until softened (do not brown). Cool completely.
Place bread cubes in a large bowl. Add cooled celery and onion mixture, parsley and fresh herbs if using.
Add chicken broth a little bit at a time just to moisten and gently stir. You may not need all of the broth (see note below). Stir in eggs.
Cover and refrigerate overnight if making ahead of time.
Grease a 5-6 qt slow cooker well. Place stuffing in the slow cooker and turn onto high for 30 minutes. Reduce temperature to low and cook an additional 3-4 hours or until hot and cooked through. If stuffing is done before your meal is ready it can remain on warm.
If using bread cubes you have dried yourself at home you will need closer to 2 cups of broth. If using dried store bought bread cubes/crumbs, you will need closer to 3 cups broth.