Preheat the oven broiler. Place the roast in a roasting pan, brush with olive oil, sprinkle with thyme leaves, and season with salt and pepper. Place under the broiler for 10 minutes, until lightly browned in several places.
Place 2 pounds sauerkraut in a slow cooker. Arrange kielbasa pieces around the edges of the slow cooker pot, and place the roast in the center. Cover with remaining sauerkraut.
Cover slow cooker, and cook roast 6 hours on High.