Make the whipped feta: In a small bowl, whisk together the feta, ricotta, and the juice and zest of ½ lime until smooth and creamy.
Prepare the spice mix: Using a mortar and pestle, crush the toasted fennel seeds. Stir in the sumac, sesame seeds, sea salt, and black pepper.
Assemble the dish: Arrange the watermelon on a serving platter. Dollop or smear with whipped feta. Sprinkle lightly with the spice mix.
Finish and serve: Drizzle generously with hot honey and garnish with mint leaves and extra lime wedges. Serve immediately.
