Season the short ribs with salt & pepper.
Add the olive oil to a large skillet over medium heat, and once the pan is hot, sear half the short ribs for about 3-4 minutes/side or until nicely browned. Transfer to a plate and then repeat for the second batch. The ribs will likely release excess fat, and if they do, spoon some of the fat out, leaving about 1-2 tablespoons in the skillet.
Add the carrots and onions to the skillet and sauté for 6-8 minutes or until they start to lightly brown.
Stir in the garlic and tomato paste and cook for about a minute, then transfer the skillet mixture to your slow cooker.
Add the red wine, Worcestershire sauce, brown sugar, smoked paprika, Italian seasoning, salt, pepper, and thyme to the Crockpot. Give it a stir. Add the short ribs in as even of a layer as possible (some will likely stick out and that's ok). Cover and cook on low for 7-8 hours or 5-6 hours on high.
Once the ribs are done, skim the fat off the surface (I just use a spoon to do this... don't worry about getting it all). Mix the cornstarch with 2 tablespoons of cold water until you've got a smooth mixture, then stir it into the Crockpot. Turn the heat to high, cover it again, and let it cook for about 5-10 minutes or until the sauce has thickened up a bit. Add extra salt & pepper if needed.