Slice watermelon in half.
Using a melon scooper, carve out the watermelon half into little balls which can go into a bowl slightly larger than the watermelon half. Save the empty watermelon half.
Gently mix the feta cheese and basil leaves in with the watermelon balls.
Add the bowl’s contents to the empty watermelon half.
Chill in the fridge for 15 minutes before serving.