Preheat oven to 200 degrees. If your oven does not go this low, set it to the lowest temperature possible. Line a baking sheet with parchment paper or a silicone baking mat. Set aside.
To the sliced berries, add the powdered sugar substitute and the avocado oil. Stir well to coat the berries. Pour the coated berries onto the prepared baking sheet and space-out/distribute into an even layer.
Bake at 200 degrees for 3-4 hours or until the berries are mostly dry. Let cool on baking sheet to room temperature. Store in an airtight container in the refrigerator.