Yes, using SecurityAssist, DataAssist, iRite and other WebAssist extensions, you could crate your own CMS System. The PowerCMS Solution Pack was created using these tools.
We do not have any tutorials that explain how to put a CMS System together, it is a somewhat complex project. You may benefit from purchasing the PowerCMS Solution Pack to see how it has been put together. If you are familiar with Database design and PHP, it should not be too dificult to examine the PowerCMS Solution and see what is going on under the hood.