Place gravy and broth in slow cooker with a cup of water and dashes of above seasonings...
place thawed roast into crock pot, slice onion in half and put inot crock pot.
Cook on high heat for 3 hours, reduce to low and cook 4 more, can cook 1 or 2 hours longer on low if desired... if you can stand the aroma!!
This pairs well with mashed pot, green peas, carrots....
When you remove the meat and slice on your platter... pour the flour mixture into crock pot to thicken the gravy, whisk in turn heat off, and within 5 minutes you have a lovely gravy.