Wash the oranges very well. Cut ½-inch off of the top and bottom of each orange.

With a sharp knife, make 4 to 6 lengthwise cuts from the top to the bottom of the oranges, just through the skin and the white pith, to the flesh. Peel the orange in these sections. If the pith is extra thick, trim some of it so that it is no more than ⅛-inch thick.

Cut the peels crosswise into ¼-inch thick pieces.

Place the orange peels into a medium saucepan and add cold water to cover by ½-inch. Bring to a boil over medium-high heat. Reduce the heat to medium-low and simmer for 10 minutes, stirring occasionally.

Drain the orange peels, rinse well, and return them to the pot. Cover with cold water again and simmer for another 10 minutes. Drain and rinse well.

In the same pot, combine 3 cups of sugar with 2 cups of water. Bring to a boil over medium-high heat and stir well to dissolve the sugar. Add the orange peel and reduce the heat to medium-low to maintain a low simmer. Cook for 40 to 45 minutes, until the syrup thickens and the peels look glossy and translucent.

Meanwhile, line a baking sheet with parchment paper and place a wire rack over the sheet.

Using a slotted spoon, remove the citrus peel from the syrup, letting the excess drain into the pot. Place it in a single layer on the wire rack set over the sheet tray. Repeat with the remaining peels. Let them dry until slightly sticky, about 30 minutes.

Place the remaining 1 cup of sugar in a wide, shallow bowl. Working in batches, add some of the peels to the bowl and shake it to coat them thoroughly with the sugar. Using another slotted spoon, remove the peels from the sugar, shake any excess into the bowl, and return them to the wire rack in a single layer. Repeat until all of the peels are coated in sugar.

Arrange the peels in a single layer so that they are not touching on a clean wire rack set over a sheet tray. Let dry at room temperature in a dry, cool area for 1 day or until dry. Store in an airtight container.