Place the beef in a bowl. Sprinkle with the salt and pepper and toss to coat evenly. In a large fry pan over medium-high heat, warm the olive oil. Working in batches if necessary, sautué the beef until browned on all sides, about 5 minutes. Transfer to a bowl and set aside.
Add the onion and garlic to the pan and sautué over medium-high heat for 1 minute. Add ½ cup of beef stock and wine, if using, and deglaze the pan, stirring and scraping up the browned bits from the pan bottom with a wooden spoon.
ransfer the beef to a slow cooker and add the onion mixture and the rest of the ingredients. Cover and cook according to the manufactureru2019s instructions until the beef is very tender and the sauce is thick but still fluid, about 3 hours on high or 6 hours on low.
Spoon the stew onto individual plates with white rice or into a large serving bowl. Garnish with the thyme and serve immediately.