Slice oranges about a half-centimeter to a centimeter thick. The thinner they are, the more transparent they’ll be, but make sure not to cut them too thinly. They’ll warp and curl if they’re thinner than a half-centimeter.

Place them on a baking pan on top of a grate so the heat can circulate around them, and place them in the oven. Bake them at 180 F. degrees (82 C.) for 4-6 hours.