Now build the main box. As mentioned, the bigger the better. Cut all the sides to the proper dimension, and plan out how you will create support system within the box using braces. THere is a lot of pressure exerted on the walls and the stronger the walls are the more efficiently the subwoofer will be able to create such low frequencies.
We used a combination of wood glue, and as few screws as possible. The box should be airtight so each screw increases the possibility of air leaks and rattling. Then we used Kwik Seal to seal all of the corners and potential air leaks.