For the crust: Preheat oven to 350 degrees Fahrenheit (175 degrees Celsius).

Whisk dry ingredients together in a bowl. Add oil, egg, and vanilla extract, if using. Knead dough until well combined. Press into a greased nine-inch (23-centimeter) pan, working the mixture up the sides. Pierce the bottom of the crust with a fork so the crust doesn’t puff up. Bake for 25 minutes, or until crust turns golden.

Combine half the orange juice with the potato starch in a medium-sized pot. Stir until potato starch is fully dissolved. Add remaining orange juice and lemon and lime juices and sugar. Stir to combine. Heat mixture and stir in egg yolks one at a time, whisking constantly so that the yolks do not clump.

Simmer over low heat, whisking constantly as the mixture starts to thicken. Cook for a few more minutes and remove from heat; whisk in oil. Refrigerate and pour into baked pie crust when ready to serve. Garnish with dried orange slices, or as desired.

Spread orange slices onto a parchment-lined baking sheet and bake at 250 degrees Fahrenheit (120 degrees Celsius) for about two and a half hours, turning once in middle. Once the oranges seem mostly dried out but still flexible, they’re ready. Remove from oven and allow to cool.

Store in a ziplock bag in the refrigerator. You can also dip them halfway into melted chocolate for another flavor and look.