Add the sugar and water to a 12-inch skillet or a large saucepan and set it over medium-high heat. Bring the water to a boil, stirring occasionally until the sugar is completely melted.

Reduce the heat to medium and add the orange slices, making sure not to overcrowd the pan.

Let the orange slices cook at a gentle simmer for about 44 - 60 minutes, until the pith is nearly translucent. Turn them over in the syrup occasionally.

Use tongs to remove the slices from the sugar syrup and lay them out in one layer on a wire rack.

Leave the orange slices to dry uncovered at room temperature for 24 - 48 hours until tacky but set.