When you make your own NTP server, you probably spend a lot of time trying to get it as accurate and stable as possible. To get good results, you need to connect your server to a good time reference, like an atomic clock, GPS or an GPSDO to get the PPS (Pulse Per Second) to sync your server with the reference clock. In both Linux and BSD, there is kernel support to slave the very inaccurate CPU clock crystal to the PPS signal, constantly adjusting the frequency, because of the cheap crystals of computers constant drift due to temperature and barometric pressure differences. So most of the work is to get a crappy crystal to behave. What if you just jumped over that step so the CPU clock is as accurate as the PPS signal and used a SI5351C Clock Generator?
Read on to see a simple way of doing it and get a extremely accurate NTP server for under $200.