I'm currently a robotics hobbyist and am full fledged in Arduino and I have used the Raspberry Pi to make some robots and PCs. Currently, I am thinking of making my own Raspberry Pi, from scratch, on a breadboard or a PCB or something. I surfed the web quite a bit and I did not get the answer I was hoping for. By making a Pi, I mean like instead of buying an Arduino, I can make one myself by buying the Atmega328, Crystal oscillators, etc. I am asking for this because my school requires me to do a project in which I make a computer or a gaming console or something like that and I would hate to look at the disappointed face of the tester all because I just bought a Pi , an connected some devices to it. Thanks in advance!
You would need to take the available SPICE and ECAD drawings, and then turn them into PCB schematics using something like KiCAD or Eagle. Then you can send the PCB file to a PCB printing service, and they'll send you what you order. You'll then have to find all the components and solder them yourself - you'll need to be very good at surface mount techniques. Honestly, unless you really need a custom RasPi, and already know how to design it, it's not worth your time to build your own IMO. Just buy one.
In terms of a school project, adding components to a RasPi is still not a simple task. These things aren't plug and play, you'll need to write the software for it, and name sure that your circuits are wired up correctly. I'm sure that your teacher will still be impressed with a 'store-bought' board used in whatever project you decide.
For future reference, this is the robotics stack exchange. I'm betting that your question is going to be closed because it is mostly unrelated to robotics. However, the electrical engineering stack exchange will probably be more than happy to help you, if you're set on building your own RasPi.