To prepare the duck, remove the giblets from inside the duck. Rinse the duck, inside and outside, with cold water. Pat dry with paper towels.
Set the duck on the working surface. Score the duck's skin on the breast in a diamond pattern, making sure you only cut the skin, without reaching the meat. Poke the other fatty parts of the duck with the tip of the knife all over, to ensure fat releases. Season the duck very generously with salt both inside the cavity of the duck and outside on the skin, legs, all over. Place the duck breast side up.
Put the chopped garlic, sliced lemons and cinnamon quills inside the duck cavity (NB:these are just for flavor, not for eating - you will discard them after cooking). The duck will have flapping skin on both ends - fold that skin inwards, to hold the garlic and lemon inside. Tie up the duck legs with butcher's twine.
Place the duck breast side up on a large roasting pan with a rack within (roasting pan should have a roasting rack to lift the duck from the bottom of the pan and allow the fat to drip below the duck).
Roast the duck, breast side up, for 1 hour at 180C. After 1 hour of roasting, flip the duck on its breast and roast it breast side down (roast the other side) for 40 minutes at the same temperature. Remove the roasting pan with the duck from the oven and carefully pour off all the duck fat juices from the roasting pan into a large glass or metal bowl. Flip the duck, breast side up again, and place back on the rack in the roasting pan.
Add to the bowl with the juices from the duck fat, combine the balsamic vinegar, honey, lemon juice with the freshly squeezed juice of 1 orange. Brush all over the duck with the balsamic mixture and cook the duck, breast side up for another 40-50 minutes at 180C, brushing every 10 minutes with the mixture.
You can carefully use the grill function in the oven to crisp up the duck skin for the last 10-15 minutes (do it carefully, checking the duck regularly to make sure it doesn't burn).
In the meantime, prepare to cook the beans. Using a pan over medium heat, add in the butter. Once melted add in the garlic and toss for a few seconds before adding in the beans to coat through.
After the duck is cooked, remove it from the oven, let the duck stand for 15 minutes. Then, carefully remove and discard the lemon from the cavity (being careful not to get burned). Carve the duck and serve with the beans as a side.