How to Make It
In a medium bowl, whisk the vinegar with the shallot, ginger and 3 tablespoons of the olive oil. Season the marinade with kosher salt. Place the watermelon in a large resealable bag and pour in the marinade. Refrigerate for 30 minutes.
Meanwhile, in a small skillet, toast the pink and black peppercorns over moderately high heat until fragrant, 2 minutes. Transfer to a spice grinder and let cool, then grind to a powder. Transfer to a small bowl and mix with the sumac and cayenne.
In a food processor, puree the feta until smooth. With the machine on, drizzle in the remaining 1/4 cup of olive oil.
Spread the whipped feta on a platter. Using a slotted spoon, remove the watermelon from the marinade and arrange on the feta. Drizzle with some of the marinade and generously sprinkle with the spices. Garnish with the herbs and sea salt; serve.