Combine the flour with several shakes of salt and pepper in a bowl or gallon ziplock bag. Add the beef cubes and toss to coat.
Place diced onion and celery into the bottom of a slow cooker. Add carrots and potatoes.
Use twine to tie together approx 3 sprigs of rosemary and 3 sprigs of thyme, and place the herb bundle into the crockpot. Add floured-beef on top.
In a large measuring cup or small bowl, stir together beef broth, wine (if using), Worcestershire sauce, and tomato paste. Pour over ingredients in the crockpot.
Cover and cook until meat is very tender (approximately 6-7 hours on high or 9-10 hours on low; cooking times may vary depending on slow cooker temps).
Add additional salt & pepper to taste.
If you'd like to thicken your broth before serving, you can do so by creating a cornstarch slurry. Simply spoon some of the hot stew liquid into a small bowl and add a tablespoon of corn starch. Stir together until blended, and then add it to the crockpot. You can repeat this more than once until you've achieved the desired thickness.