1. Cut stew meat into 1 1/2 inch cubes and place in slow cooker with sea salt.
2. Peel and quarter onions. Slice potatoes in half. Peel carrots and cut into 1-inch chunks.
3. Add onions, mushrooms, potatoes, carrots, garlic, wine, and bay leaves to slow cooker.
4. Tie half of thyme with a string and add to the slow cooker. Remove leaves from remaining thyme stems, chop, and reserve for garnish.
5. Cook on low for 6-8 hours, until the meat is very tender. Remove and discard thyme bundle and bay leaves when finished.
6. Carefully pour liquid from slow cooker into a saucepan.
7. In a small cup, whisk cornstarch and water to make a slurry. Add about a third of this liquid to the saucepan and simmer for a minute or two. Add more slurry if you wish to have a thicker sauce, but go easy as too much will make your sauce too gelatinous.
8. Season the sauce with sea salt, then pour it over the meat and vegetables.
9. Serve stew with chopped thyme.