Pat the beef dry and season it with salt and pepper. Heat the olive oil in a large skillet over medium-high heat, then brown the beef in batches until all sides are seared.
Sprinkle the smoked paprika over the browned beef and stir for 30 seconds to coat the meat. Transfer everything to the slow cooker.
Add the onion, carrots, garlic, sweet potatoes, Guinness, beef broth, and thyme to the slow cooker. Stir gently to combine.
Cover and cook on low for 7 to 8 hours until the beef and sweet potatoes are fork-tender.
In a small bowl, whisk the flour with 3 tablespoons of the cooking liquid until smooth. Stir the mixture back into the stew and cook on high for 20 minutes to thicken.