Preheat the oven to 220 degrees Celsius.
Remove the turkey breast from the refrigerator and allow it to come to room temperature before stuffing. Using a meat mallet, lightly bash the thickest sections of the turkey breast to flatten it a little. Spread the breast flat, skin side down ready for stuffing.
Mix the oats with the onion, sage and oil and season with sea salt and pepper. Spoon the stuffing along the length of the breast and roll the meat over to cover it completely.
Using kitchen string, tie the breast securely to ensure the stuffing is not lost in the cooking process. Tuck thyme springs under the skin and brush with corn oil. Season and place in a baking tray.
Cover with foil and place in the oven to cook at 220C for 20 minutes.
Reduce the heat to 180C and cook for a further 30 minutes.
Remove the foil, increase the temperature to 200C and cook for a further 25 minutes basting regularly. Remove the turkey from the oven and leave to rest for 20 minutes before carving.
To make the gravy, while the turkey is resting, drain the roasting pan of all the juices into a small pan. Add the flour and stir continuously. Add the chicken stock and continue to stir until the gravy thickens. Season and serve over the turkey.
Note: Steel Cut oats are coarsely cut oat grains that resemble hard breadcrumbs. They are available from good health food stores.