Preheat to 325°. Lightly oil a large gratin dish or a baking dish (9 x 13 inch works well).
Peel off and discard any bruised or ragged outer leaves from the cabbage. Cut cabbage in half, then into 8 wedges. (Don’t trim away cabbage heart.) Arrange wedges in the baking dish on their sides, overlapping a little but trying for a single layer. Scatter the onion and carrot over the cabbage. Drizzle with stock or water and the fat. Season with salt, pepper, and pepper flakes. Cover tightly with foil and place in the oven.
Braise for one hour. Uncover and gently turn the wedges with tongs, keeping them as intact as possible. Add a bit of water if the pan is drying out. Cover pan and return to oven. Bake one hour.
When cabbage is completely tender, remove foil and increase heat to 400°. Roast until vegetables begin to brown, about 15 minutes. Serve warm or at room temp.