Cut slits into the roast just to place smashed garlic in. Cover all sides with seasoning salt.
Place onions, ketchup, half of brown sugar, vinegar, Tabasco, and liquid smoke into crock pot and stir together.
Lay roast over the sauce and spoon sauce from sides over top of the roast.
Cook on low for 8 hours or high for 4 hours. After roast is cooked, tear apart meat to shred and then stir into sauce. Add additional seasoning salt and remaining brown sugar. Stir together and remain on low till ready to eat.
Serve on buns. Creamy slaw is a great topping to the sandwich.