Hello Chris,
unlike as you said "simple ICs" FPGA have most of their pins user configurable. There is little sense in giving application circuits, cause these pins can have nearly any function the developer want's them to. Some pins are dedicated, e. g. for configuration purposes. Example circuits for these pins can be found in device manuals and detailed application notes. Other documents discuss PCB design issues or special type of interfaces, e. g. for DDR-RAM.
The evaluation board documents, including layout files for some boards, are however a good starting point when you are planning a similar design. To my opinion, you should be able to design a FPGA board from the scratch, I did it myself some years ago and several times helped customers to take the first step.
But FPGA are rather complex and there are some design traps you may walk in. Thus it may be an alternative to start a prototype design based on an evaluation board. Some have daughter board connectors where your hardware could drop in. You can start code development on the evaluation platform and design your own board in parallel. If it isn't operational from the beginning (very likely) you have a reference to compare with.
Regards,
Frank