It depends on how advanced NAS you want. Just installing Raspberry Pi OS and add Samba so you can share files with Windows/Linux/Mac computers is quite trivial, 10-30 minutes work. See
https://www.raspberrypi.com/tutorials/nas-box-raspberry-pi-tutorial/
If you wish a more advanced NAS you can pick a NAS distribution and then you get Web management and more features integrated in one place, the Web interface.