In a small bowl, mix together the seasoning salt, garlic powder, Italian seasoning, onion powder, and black pepper. Rub the mixture thoroughly over the beef roast, making sure it's fully coated.

Heat a frying pan over high heat and add the oil. Sear the roast on all sides until it's evenly browned, then transfer it to a 4-6 quart slow cooker.

Using the same pan, reduce the heat to medium and sauté the chopped onion until softened and translucent. Stir in the beef broth, tomato paste, balsamic vinegar, Worcestershire sauce, and honey. Let the mixture simmer while scraping the browned bits from the bottom of the pan to enrich the sauce.

In a separate small bowl, whisk together the corn starch and water until smooth. Stir this mixture into the pan and cook for another 2-3 minutes on low heat, stirring constantly, until the sauce starts to thicken.

Arrange the baby potatoes and sliced carrots around the roast in the slow cooker. Pour the thickened sauce over the top, ensuring the roast and vegetables are evenly coated.

Set the slow cooker to low and cook for 8 hours, or on high for 4 hours if you need a quicker option. For vegetables with a firmer texture, add them halfway through the cooking time. The roast is done when it easily shreds apart, and the potatoes are tender.

Once cooked, remove the roast from the slow cooker. You can either slice or shred the meat. If desired, stir in the optional ketchup to brighten the sauce after the long cooking time. Serve the roast and vegetables with the rich juices. To further thicken the sauce, transfer it to a small saucepan and whisk in additional corn starch slurry over low heat until it reaches your preferred consistency.