Prep the leaves and cucumber. Add lemon juice and garlic to sugar and whisk together.
Toss dressing with leaves and cucumber, leaving aside a tiny amount of dressing. It's quite watery, but you will end up using it all.
Place watermelon in an aesthetically pleasing manner to your liking around the bowl (tossed, it likes to sink to the bottom). Crumble feta if using over the top. Lightly coat with remaining dressing.