Source: This Jess Cooks
Drying with a dehydrator:
If using a dehydrator, transfer the orange slices to the dehydrator after simmering. Set to 60°C and dry for 3-4 hours. Remember the slices should be slightly tacky and not completely hardened or dried so the granulated sugar will stick. Drying times will vary based on the thickness of your slices.
Drying in the oven:
If you want to dry the slices in the oven, transfer the simmered slices to a parchment paper-lined baking sheet. Set the oven to 95°C and dry for 1-3 hours, flipping every 30 minutes to check the dryness. Remember the slices should be slightly tacky and not completely hardened or dried so the granulated sugar will stick. Drying times will vary depending on the thickness of your slices.
To make Chocolate Drizzled Orange Slices, once the slices are dried, place them on a parchment paper-lined baking sheet. Drizzle with melted dark chocolate and sprinkle with flaky sea salt. Transfer the baking sheet to the refrigerator for 15 minutes for the chocolate to firm, then enjoy.