Chop onion and garlic. Put in crock pot and set roast on top. Sprinkle with salt, pepper, rosemary, and thyme. Pour in the wine. Cover and cook on high setting about 5 hours.
Remove roast to serving plate. Measure 2 cups of the cooking liquid into a saucepan.
Stir together the flour and water and stir into the cooking liquid. Bring to a boil, stirring. Reduce the heat and simmer 10 minutes. Slice the roast and serve with the gravy.