Where are the boxes going to be stored? Are you going to slide them under the bed, on a shelf or closet or on the the floor? Also, how big will they be.
Easiest access will be a simple hinged lid and latch of some kind. If the box is relatively large, the sliding lid would a be a pain because you need twice the size of the box to slide the lid out and to get at the contents at the end. The easiest way to make a sliding lid is to cut a groove slightly wider than the thickness of the top, using a router or table saw with dado blade.
--Nathan, TX. Hire the lazy man. He may not do as much work but that's because he will find a better way.