Place the roast, water, onion soup mix, and celery salt in a crock pot and cook on low for 4-6 hours.
Once the roast is done, place it on a platter, cover it and set aside.
Place the garlic bread of your choice and bake on a baking sheet as instructed on the package.
In a saute pan melt the butter on medium heat. Once the butter is melted add the flour and whisk to combine making sure to break up any lumps. Once the flour is completly incorporated into the butter pour the beef broth from your crock pot into the saute pan making sure to whisk it as you add the broth so that there are no lumps in the gravy. Cook the gravy on medium heat whisking it occasionaly to keep it from sticking at the bottom of the pan.
While the gravy is cooking, start shredding your beef in about 2 inch chunks. Once the gravy has reduced by half add the chunks of beef in with the gravy and carefully stir to combine.
The garlic toast should now be done, pull it out of the oven and set aside.
Once the gravy and beef have come back to a simmer, place a slice of garlic toast on each serving plate and top them with about 3 tbsp of the beef and gravy and serve.
Note: I serve these sandwiches with mashed potatoes and a vegetable medley but they are perfect served as just a sandwich. I have also added sauteed onions to the gravy while it reduces which also is wonderful.