Peel and cut carrots into 1-3" pieces.
Peel and cut onions into 1-3" pieces.
Wash and cut potatoes into 1-3" pieces.
Mix together salt, pepper, thyme and tarragon.
Rub roast with olive oil and cover with about 2/3 of spice mix.
Heat skillet over medium high heat and brown on all sides.
Transfer roast to slow cooker.
Lightly coat vegetables in olive oil and season with remaining spice mix.
Transfer vegetables to slow cooker.
Add some stock to skillet and stir to deglaze.
Pour liquid into slow cooker.
Add remaining stock to slow cooker.
Cook on high for 5 hours or low for 10 hours until vegetables are tender and meat pulls apart easily.
Transfer meat and vegetables to serving dish.
Pour liquid in sauce pan. and heat.
Mix cornstarch with an equal amount of water and stir until well blended.
Add cornstarch mix to sauce and heat, stirring frequently, until sauce thickens.
Pour sauce over meat and vegetables.