Cut the beef into bite-size chunks. If you're using grass-fed beef, be sure to leave all the fat on, as grass-fed beef tends to be lean and you're going to want all those fat drippings in the stew. Place in a 6-quart slow cooker.
Sprinkle the lavender blossoms, dried thyme (if using), salt, and pepper over the beef cubes.
Combine the stock and wine and pour over the beef.
Layer the remaining ingredients over the beef in the order listed and do not stir. Lay the fresh sprigs of thyme and rosemary on the top.
Cook on high for about 6 hours or on low for 7-8 hours until the vegetables and beef are very tender.
About 10-15 minutes before you want to eat (or just as you're setting the table), combine the flour or arrowroot powder with 1-2 tablespoons of water - just enough to make a pourable slurry. Pour it over the stew and stir gently so as not to break the potatoes and carrots. Return the lid and let cook until ready to serve.