Wash and pet dry the oranges, then slice each to 1/inch thick slices.
In a 16-inch wide saucepan, measure 2 cups (400g) of sugar, then pour over the water.
Place over the stove top and cook over medium-high until the sugar has completely dissolved. Do not stir the sugar, if needed swirl the pan. Stirring the sugar might cause it to crystalize.
Line the orange slices in an even one layer in the sugar syrup. Cook until it reached a boil.
Reduce the heat to low and simmer for 45 minutes.
Transfer the orange slices over a wire rack and let them chil for 5 minutes.
Place the remaining cup of sugar (200g) in a wide bowl, then coat each slice with sugar.
Place the coated orange slices back over the wire rack, let cool completely, then store in an airtight container for up to three weeks at room temperature.