Cut the benchtop slats from treated or cedar decking (or composite if you prefer). Attach the slats over the first two bays by driving a pair of deck screws into each slat end and the cleat below. Do not fasten the deckboards over the right end bay. Drill 1" finger holes near the end of each board and simply set them on the cleats so they can be removed to access the shelf below. If you wish, coat the bench with deck finish.