some people will say plywood is fine but you should make sure its pretty thick. i myself like to use 3/4" MDF. just make sure you use wood glue or liquid nails when joining pieces of wood. and on the inside after the glue is dry, you should caulk all the seems to completly seal it. to tune a box, you just have to make your port length longer or shorter. there are calculators out there to help you do this.
you can use wood glue then put screws in it about every 5 inches or so but make sure to pre-drill. unless you have some big clamps, you dont need to screw it together. and if you have a sealed box, you dont/cant tune it.