Place the olive oil, rosemary, thyme, salt, pepper, garlic, and dijon mustard into a bowl. Mix until they are well combined. Using your hands rub on all sides of the roast.
Add some olive oil into a preheated pan. Place the roast in and sear it over medium high heat for 3 – 4 minutes on all sides. Remove the roast and set it aside in the slow cooker liner.
Pour about 4 – 5 tbsp of water into the pan in the pan, and deglaze it over medium heat. Pour the contents of the pan over the roast in the slow cooker liner. Set it aside in the fridge overnight. Alternatively, you can place it into the slow cooker immediately.
Place the liner in the slow cooker, turn the heat on low, and allow it to cook for 6 – 7 hours on low. If you are in a hurry, you can cook it on high for 4 – 5 hours.
Remove the roast and set it aside to rest. In the meantime, pour the remaining juice from the slow cooker into a pan. Bring it to a boil. Add in the diluted corn starch while stirring constantly until it thickens.
Slice the roast, place it on a plate, pour the gravy over the top. Serve your slow cooker roast beef up with some mashed potatoes and the vegetable of your choice.
