place the sliced onions in the crockpot and then place the roast on top.
in a small bowl, mix chili sauce, brown sugar,dry mustard, pepper, paprika and salt. Pour over roast. Cover and cook on low for about 6 hours or until fork tender; you should be able to pull apart with two forks.
Remove the meat and shred. Place shredded meat back into liquid in crockpot. Serve with coleslaw and a squeeze of ranch dressing.