1. Combine orange juice, marmalade and honey in a bowl deep enough to hold the duck. Add duck, cover and refrigerate for 8 hours, turning duck once or twice.
2. Preheat oven to 190 C.
3. Remove duck from marinade, reserving marinade. Prick duck skin all over with a fork (do not pierce the flesh), and season inside and out with salt and pepper. Place breast side up on a rack in a roasting pan and transfer to oven. After 10 minutes, turn heat down to 175 C and roast for 1 ½ hours.
4. Once duck has rendered some fat, spoon 2 tablespoons of it into a saucepan. Heat over medium-high heat, add onion, and sauté until tender and light brown, 5 - 6 minutes. Sprinkle flour and cook for 1 minute to lightly colour, stirring occasionally. Pour in reserved marinade and bring to a boil over high heat, stirring up any browned bits. Adjust heat to medium and reduce liquid until thickened, 20 – 25 minutes. Pour sauce into an electric blender or food processor and puree until smooth. Pour through a strainer and set aside.
5. When duck has roasted for 1 ½ hours, remove pan from oven and turn heat down to 160 C. Discard all but a little fat from roasting pan, and lay orange slices over bottom of pan. Return to oven and cook until orange slices begin to brown, about 10 minutes. Remove orange slices and duck from pan, and let stand for 10 minutes while finishing sauce.
6. Cut into portions using sharp scissors.
7. Place each duck portion on a plate, serve with rice, orange slices and ladle on sauce.