Preheat oven to 375 F.
Toss the bread cubes with the melted butter, garlic, and sea salt. Spread the seasoned bread onto a sheet pan and bake for 10 minutes at 375 F, or until the tops are starting to brown.
While the croutons are baking, crumble and cook the sausage in a medium-sized pan over medium heat until it's evenly browned. Add the celery and onion. Stir to combine and continue cooking until the celery and onion starts to wilt. Turn off heat and set aside.
Once croutons are finished baking, reduce oven heat to 350 F. In a large mixing bowl, combine the croutons with the with cooked Italian sausage crumbles, celery, onion, rosemary, sage, and thyme.
Pour the stuffing mixture into a 9" x 13" baking dish, pour bone broth over top, and bake for 30 minutes, or until the top is golden brown.
Let cool 5-10 minutes and serve!