Preheat oven to 350°F. Grease or butter a large casserole dish or 9x13" pan.
If you're using a chicken-style vegetable broth which comes in powder or bouillon form, prepare it ahead of time by whisking into water just off a boil.
In a large skillet over medium-high heat, melt vegan butter. Sauté onion and celery until tender and fragrant, about 3-5 minutes. Add in garlic and sauté for an additional 2-3 minutes until onions are just beginning to brown.
Transfer bread cubes to a large mixing bowl. (You can technically mix directly in the casserole dish, but it's easier with a very large bowl.) Pour the onion mixture over the bread cubes. Sprinkle poultry seasoning and fresh herbs over bread mixture and toss to distribute vegetables and herbs.
Gradually pour in vegetable broth a little bit at a time, gently tossing between additions. You may need a little more or less broth than the amount listed — it will depend on how dry your bread is. White breads (like French or Italian bread) tend to require less broth, while a crusty loaf (like a rustic sourdough) will require more. Add enough broth to moisten all of the bread without making it soggy.
Give the stuffing a taste and season to preference with salt and pepper.
Transfer to prepared casserole or pan. Cover with foil and bake for 35 minutes. Uncover and bake for an additional 10-15 minutes depending on how crispy you like your stuffing.