Lay a piece of cheese on each slice of bread, then top with a few spoonsful of smashed blackberries. Gently pick up 3 slices, brush some olive oil on the bottom, and place them on the griddle or skillet. Place the remaining slices on top, brushing them with olive oil too. Cook low and slow so the bread gets perfectly golden and the cheese melts, about 4-5 minutes on each side.