Watermelon Frose

1 Pour the wine into ice cube trays and freeze until firm, at least 6 hours (they will still be a bit icy / slushy).
2 Cube watermelon and freeze on a parchment paper-lined sheet pan until firm, at least 4 hours.
3 When the wine and watermelon cubes are frozen, you can transfer them to a plastic bag and freeze for up to a month.
4 Make the simple syrup by combining sugar and water. Heat them on the stovetop or in the microwave until the sugar dissolves.
5 When ready to serve, transfer frozen wine and watermelon to a blender and blend until smooth. (I had to let them defrost at room temperature for a few minutes before they would blend.)
6 Add simple syrup a bit at a time, tasting as you go. Depending on the natural sweetness of the wine and fruit, you may just need a little or none at all.