Preheat the oven to 400°F. Heat two tablespoons of canola oil in a heavy cast iron skillet over medium-high heat (about 400°F) until hot but not smoking. Season the boneless beef chuck roast cubes with a pinch of salt pepper and place them in the skillet in a single layer without crowding. Sear the meat for exactly 2 minutes per side without moving it so a deep mahogany crust develops. Transfer the seared beef into your slow cooker liner and leave the remaining fat in the hot pan. (I tried skipping the sear once, the gravy came out flat and pale, so don't skip this step.) Sear hot and quick, builds the rich fond for flavor.

Pour half a cup of low-sodium beef broth directly into the hot skillet while keeping the heat on medium. Use a wooden spoon to firmly scrape up all the dark browned bits stuck to the bottom of the pan. Simmer the liquid for 60 seconds until it turns dark brown and slightly glossy. Pour this rich deglazing liquid straight over the seared beef in the crockpot. Deglaze while hot, lifts the caramelized fond into the gravy.

In a medium bowl, whisk together the brown gravy mix packet, onion soup mix packet, canned condensed cream of mushroom soup, worcestershire sauce, and the remaining 1 cup of beef broth. Stir vigorously for 30 seconds until the mixture is smooth and free of large lumps. Pour the gravy mixture evenly over the beef in the slow cooker liner so every piece is submerged. Cover the slow cooker tightly with its lid. Whisk completely, prevents powdery lumps from forming in the sauce.

Set the slow cooker to LOW heat (around 190°F) and cook for 7 hours without opening the lid. As it cooks, the tough connective fibers in the chuck roast break down completely. You'll smell a rich roasted beef aroma throughout the kitchen, and a fork inserted into a beef chunk will twist easily with zero resistance. If you pull the beef too early, the meat will stay chewy and tough. Cook on LOW for 7 hours, lets the collagen dissolve into tender gelatin.

Mix 2 tablespoons of cornstarch with 2 tablespoons of cold water in a small glass until completely smooth. Stir this slurry directly into the bubbling slow cooker gravy around the beef. Cover and cook on HIGH for an additional 15 minutes until the gravy thickens to a glossy velvety coating that clings to the back of a spoon. If you skip the slurry, the gravy will remain thin and watery. Boil with cornstarch slurry, activates starch gelatinization to thicken sauce.