Marinate in spices at least 10 minutes, though several hours is better.
Brown meat on all sides in a skillet on medium-high heat to lock in juices. (optional step that enhances flavor)
Place roast along with sliced onions and 1-1.5 cups of water or beef broth in a crock pot.
After two hours, add carrots and sweet potatoes to crock pot. They can be added at the beginning but they will be much softer at the end.
Cook for 4 hours in the crock pot on low.
Let sit 10 minutes before cutting. Slice against the grain.