This is how I set up my network:
Is everything done right, it will work forever without losing the positions to each other. No extra mods are required (but KerbalAlarmClock is helpful).
I use a carrying system with a set of 4 relays. The relays are all equal and that's important: Same weight and same fuel = same DeltaV.
The Sepratrons are facing away from the remaining ship, otherwise the carrier would end up with a different orbit. The Stack Decoupler force is set to 0% for the same reason.
Achieve circular orbit. No need to be too accurate here.
Warp to Apoapsis, turn Prograde and activate the first relay.
2-3 orbits later it's time for the next relay and so on (always exact on the Apoapsis).
The result is a system of 4 relays with identical orbits.
Ok, it is not a beauty, but even after 12 years of time warp the system remains functioning and this was my main goal