I posted a box pattern made from 1/4" plywood some time back. The size is different, but you could use that as the basis and draw your own out easy enough. Graph paper with 1/4" or 1/8" divisions can be printed from here:
http://incompetech.com/graphpaper/multiwidth/Here's a box - it was kind of plain so I added an intarsia butterfly:
Posting with pattern:
http://stevedgood.com/community/index.php?topic=12869.0Another posting of a similar box with a top design. Top is 2 layers thick - top is rose cutting, bottom is painted red and green.
http://stevedgood.com/community/index.php?topic=12909.0Another made in cedar: top is 2 layers - bottom is a snug fit into the box opening.
http://stevedgood.com/community/index.php?topic=14550.0A trick I used with the cedar box was to take the intersecting sides (like front and one side), tap them flat together, then cut in from the edge to the depth of the finger (wall thickness plus a little). Then cut out the fingers in alternate positions on the front and side. Repeat for each corner. That way the fingers and openings are guaranteed to line up. Tests show that modern glue will make the fingers break before the joint will separate. Then sand the extra off with a curved corner. You don't need a lot of fingers between the sides and bottom - maybe just one on the 3" side and 2 on the 6" side.
If some voids show up, mix some fine sawdust (from a sander, not from the saw) and wood glue to a paste and fill them in. Use a credit card to squeegee the paste into the void.
Good luck.