Mix the cornstarch with 1 tablespoon orange juice in a small bowl.
Combine the huckleberries, orange zest, 2 tablespoons orange juice, sugar, and spices in a medium saucepan.
Bring to a simmer over medium-low heat and cook until the berries begin to burst and become juicy, about 8 minutes.
Stir in the cornstarch slurry and continue to cook until the sauce thickens, about 1 minute.
Remove from the heat and let the sauce cool slightly. Transfer to a lidded jar or container and let it cool completely before stashing in the fridge. The sauce will thicken more as it cools.
Notes
Thinning the sauce--If your sauce thickens too much, stir in extra orange juice or water, 1 tablespoon at a time until you reach your desired consistency.
Storage and freezing--Store in a sealed container in the fridge for up to 2 weeks or freeze for up to 3 months.
Dietary--This recipe is suitable for gluten-free, dairy-free, and vegan diets.