There may be carpenters sitting back and chuckling at the idea that they would ever actually buy a cornhole board; given that it is essentially giant pieces of wood constructed together with openings throughout. Of course, even some homeowners may be confident that they could build a cornhole board that would suffice enough for small uses. The reality is this option is always open to you as you can make a custom cornhole experience. However, you still need to buy the wood and put forth the effort of making it.
It just seems logical to buy a professionally crafted version, even if you know you could make it yourself. The plus side to this, also, is a pre-made board will abide by official regulation sizes and slopes. The beanbags need to land on or in the board, after all, and professionals tailor their boards for just that purpose.