I personally cant, but there is a good resource on the site for it. If you got to the coops tab, there is an incubator section of a bunch of different homemade incubators. You can look at those, some are a little more detailed than others, but they all have good ideas and information. If you find one you like and would like more information, you can comment or PM the creator, and they are usually more than happy to help.
Dan I'd like to add that the styrofoam incubator itself isn't bad. It is likely the cheaper parts that most have in them. The GQF 1588 is a good styrofoam incubator that a lot of members on here get very successful hatches out of. I know where you are coming from though. My first homemade incubator was because of how sorry the little giant/ farm innovators still air models were.
I have a farm innovators fan model that works great, it is not very old maybe it will eventually fail, but until then I say it works great. I want to build an incubator too but only because I want to hatch more eggs