This Independence Day, watch the fireworks while nibbling on a picnic chock-full of summery produce. Set up camp on the beach, in the park, or wherever the show may be, and enjoy a menu of salads that travel well and stay fresh all day long. Supplement your entrees with salty potato chips, icy tumblers of cucumber gin cooler, and a dessert of colorfully layered summer trifle in individual mason jars—storage and serving vessels in one.