Heat the oil in a heavy saucepan. Add the bacon and sauté until the fat runs, then add the diced onion and carrot and sauté until soft. Add the flour and cook gently, stirring, until the roux is a rich dark brown, about 5 minutes.
Bring the stock to a boil. Remove the roux from the heat, let it cool slightly and whisk in three-quarters of the stock. Bring to a