NBeed help building a Box

[insane-Snake]

i'm making a Box for my sony XS-l121p5 12" sub....but i must also make it fit behide the seat of my reg. cab 98 silverado..how would i go about making that....the specs for the Sub is:
Width: 11 in
Depth: 6.375 in
Diameter: 12 in
Thx for any help given :toast:

~Garrett~

[infrabass]

Measure the part behind the seat if you want any help.

[insane-Snake]

the part behide the seat is about 11-15 inchsfrom the back of the seat till the cab. from side to side theres about 4 ft or so