Use a sharp knife and cutting board to cut the watermelon into four thick, even slices about 1 inch thick. Place the slices on a plate and set aside.
4 thick slices watermelon
Preheat the grill to medium-high heat. Use tongs to carefully clean the grill grates, then brush the grates with a little oil to prevent sticking.
4 thick slices watermelon
Using a basting brush, lightly coat each side of the watermelon slices with olive oil. Optional: sprinkle with a pinch of salt for added flavor.
4 thick slices watermelon
Place the slices onto the hot grill. Grill for about 2-3 minutes per side, or until you see clear grill marks and slight charring. Flip the slices carefully with tongs. The watermelon should develop dark grill marks and start to soften.
4 thick slices watermelon
Once grill marks are prominent and the watermelon has softened slightly, remove the slices from the grill and place them on a serving platter. Let rest for 1 minute.
4 thick slices watermelon
Serve immediately, optionally drizzled with extra olive oil or a sprinkle of salt. The watermelon should be juicy with a smoky aroma and slightly caramelized surface.
4 thick slices watermelon