Optional- Sear the roast first.Heat a pan over medium-high heat. Add 1 tablespoon of oil. Sear the roast until browned on both sides.
Place roast in 6-quart slow cooker.
Sprinkle gravy mix, ranch seasoning, and Italian dressing mix on top.Sprinkle with black pepper and crushed red pepper flakes.Pour water on top of roast.
Cover slow cooker and cook on LOW for 8 to 9 hours.
Remove the roast and place on a serving platter. Tent with foil to keep warm.Whick together cornstarch with cold water and whisk into liquid in slow cooker. Cover and cook on HIGH for 20 minutes to thicken.Note: To do this step faster, transfer to a pot and bring to a boil over high heat on the stove. Let simmer for 1 minute.