Scrub orange skins lightly so that they are smooth. Make sure that any black spots on the skin are removed.
Quarter each orange without entirely separating it—leave about ¼ in/6mm intact at the bottom. Remove the seeds and place 1 tablespoon of them in a cheesecloth, tying the corners so that the seeds do not fall out. Soak in 3 cups/720ml water, setting aside