Extremely Long Prototyping Board for LED Strip
If you want them 2 inches apart, you could punch the leads thru cardboard and solder them together with the resistors on the back.

If you're asking about off the shelf true prototyping boards, many of the common "solderless breadboards" can snap together to make any length and width you want.  

However, with 24 LEDs spanning 4 feet, I'd want something more permanent.  I think the cardboard trick with maybe a wooden dowel glued to the back for stiffness would do it.