Preheat your oven to 200 degrees F. Line a large baking sheet with parchment paper. Set aside.
Remove the stems from the strawberries. Then cut them into slices, either widthwise or lengthwise.
Place the strawberry slices on the prepared baking sheet, leaving some space between each slice. You will want the air to be able to flow easily between the strawberries. Sprinkle with sugar, if desired. (see note)
Bake for 2 hours. Take the baking sheet out of the oven, and flip the berries over. Bake for another 2-3 hours until sufficiently dried.
Remove the strawberries from the oven and allow to cool completely. Then transfer them to an airtight container and store for up to 5 days. (There are no preservatives, so they should be consumed promptly.)
Notes
Taste a strawberry slice once you've cut the berries. If they're pretty sweet already, you can skip the sugar. If they're more tart, feel free to sprinkle the slices with 1-2 tablespoons of sugar.