Cut the oranges into ¼-inch thick rounds using a sharp knife or mandoline.
Combine the sugar and water in a saucepan and bring to a boil while stirring until the sugar dissolves completely.
Lower the heat to maintain a gentle simmer and carefully place the orange slices in a single layer in the syrup.
Let the orange slices simmer for 45 to 60 minutes, flipping them now and then, until the peel looks clear and translucent.
Use tongs to lift the slices from the syrup and spread them out on a wire rack.
Allow the slices to air dry uncovered at room temperature for one to two days until they are tacky yet firm.
For extra sparkle, toss the slices in granulated sugar or dip them in melted chocolate and sprinkle with flaky salt as desired.
