In a large bowl, combine ground beef, breadcrumbs, milk, onion soup mix, and dried thyme. Mix until combined, then shape into 8 patties.
Arrange sliced onion in the bottom of a slow cooker.
In a large skillet over medium-high heat, heat the olive oil. Dredge patties lightly in flour, then brown on both sides.
Place browned beef patties on top of sliced onion in slow cooker, stacking alternately.
Stir together condensed soup, water, and au jus packet and pour over beef patties. Cover and cook on low until beef is cooked through, 4-5 hours.
