secure.
the side panels are made similar to cabinet doors. i used my raised panel router bits to make the side panels, but you can do the same thing with a table saw or a straight router bit, minus a few curves.
the front and back stiles (27″ vertical pieces) only need a 1/4″ wide groove cut 3/8″ deep down the center. you can do multiple passes on the table saw with the blade 3/8″ high or with a 1/4″ straight router bit on a router table.
the top and bottom rails (15″ horizontal pieces) also need a 1/4″ wide groove cut 3/8″ deep down the center. on each end of the stiles 