1. Preheat the oven to 200ºF (93ºC). Remove the zest of the oranges using a vegetable peeler, and spread them on a baking sheet. Dry in the oven for about 50 to 60 minutes, stirring them once or twice during drying. They don’t need to be bone-dry when done, but should have lost most of their moisture and smell orangey.
2. Pour the liquor into a clean medium jar. Add the orange peels and spices. Cover and shake. Let the jar stand in a cool, dark place for 2 weeks, shaking it once daily.
3. Strain the mixture through a coffee filter. Stir in the caramel, if using, then bottle.