Preheat oven to 250 F.
Cut bread into rough 1 inch chunks then scatter in a single layer on a baking sheet.
Stirring occasionally, bake until dried out, about 1 hour. When done, let cool on baking sheet.
Preheat oven to 375 F.
Melt butter in large skillet over medium-high heat. Add the onions and celery and cook until just beginning to brown, about 10 minutes.
Transfer dried breadcrumbs to a large mixing bowl. Add cooked onion and celery to breadcrumbs and toss to combine.
In the same pan the onions and celery were cooked in, add the broth, parsley, sage, rosemary, and thyme. Stir and let simmer 1-2 minutes.
Drizzle in broth 1/4 cup at a time and toss. Continue until all broth has been incorporated. Salt and pepper to taste.
Transfer to a 9 x 13 baking dish and bake until crisp and golden on top, about 20-30 minutes.