Slide a cube of watermelon onto a skewer, followed by a square of havarti cheese and a leaf of basil. Repeat this pattern twice more and then finish with one more cube of watermelon. Each skewer should have 4 cubes of watermelon, 3 slices of havarti cheese, and 3 leaves of basil.
Place all of the skewers on a platter, drizzle with olive oil and sprinkle with flaky salt. Serve immediately.