In a skillet set over medium-high heat, heat a drizzle of oil and brown the beef in batches, sprinkling with salt and pepper.
As the meat browns, transfer it to the bowl of a slow cooker. (If you want to skip this step, toss the meat directly into the slow cooker.)
Sprinkle with flour and stir to coat.
Add the stock, wine or beer until the liquid almost covers the meat.
Add the balsamic vinegar, tomato paste and toss in a sprig of rosemary or thyme from the stew mix package.
Cover and cook on low for 5-6 hours, then stir in the stew mix and cook for another hour, or until the vegetables are just tender.