/diy/ - Do It Yourself

Hello /diy/. I am not a great /diy/er. I have an empty space between two cabinets underneath a desk and wanted a bookshelf there. Halfway through taking measurements and drawing planes that would "match" the dimensions of the space, inner/outer diameter started to exist in my brain and I realized my idea was retarded and would make something wrong (it's just a shelf so doesn't "really" matter but still). If I have this to someone who actually uses their entire brain for things, would they be able to cobble someone together when they got done laughing?