Bring orange juice to a simmer with the cinnamon, star anise, and saffron until the spices start smelling fragrant.
Make a slurry of the potato starch, powdered sugar, and water and then add to the orange juice mixture.
Once everything is well combined, bring it off the heat and allow to cool down to room temp. Add the sliced oranges and chill for approx 2 hours.
When you're ready to serve, add ice cream/whipped cream if desired!