First thing, know what you want. Are you looking for quality, or loud? The easiest sub box almost anyone can make is a sealed cube. So you need to know what the recommended size for the enclosure is, this will be highlighted in the subs specifications. Most 10" are .5 cubic feet to .8 cubic feet. so now some basic dimensions you can start off with a 12"X12"X12" this is 1 cubic foot. Now it isn't bad to have more space in a box than you need, but it still needs to fit in a given space. To calculate cubic feet you take the inches in this case 12" for all three basic dimensions(Width, Height, and Depth) and mulitply them together. Whe you do this you'll get 1728 inches cubed. Now you'd have to divided by 12 three times to get cubic feet. But we know it's one since we already multiplied by 12 three times. This is a basic box that will be okay with any sub you've described. If you want different dimensions mulitply the three dimensions together in inches and divide by the 1728 and this will give you cubic feet. Remember this is going to be your inside dimensions. Have any odd shapes you want to build or more questions ask. Hope this helps.