Here's a file from Bass Box Pro and a quick hand sketch
Some notes about the design:
6cf tuned to 30hz is a low end monster, don't expect much out of it above 55hz
The sub will be able to take rated power down to around 25hz and it still doesn't hit xmax so you don't need a subsonic filter unless you play below 20hz
The window brace is to be placed in the middle of the box and cut to 3/4 thickness. This is very crucial to the rigidity of the box, do not skip out on this! If you don't know what a window brace is, google it.
You will need 1x 4x8 sheet + a 2x2 panel for all of the pieces.
Panel sizes:
Top 34 x 23 inches
Bottom 34 x 23 inches
Front 34 x 16.5 inches
Back 34 x 16.5 inches
Left 16.5 x 21.5 inches
Right 16.5 x 21.5 inches
Window brace 16.5 x 21.5 inches
View attachment 19329