Abstract: This is not my original idea, but it is refined by me, according to my experience; I saw this idea in two places, just giving credit: Solution for Failure To Communicate in Prison Architect: Xbox One Edition
. This solution assumes decent knowledge of this game.
Start a New Game in Warden Mode, Ironfort Map (Map 9). Choose any Warden you want, set Starting Funds to Unlimited and enable Gangs. This will turn the Difficulty to custom and that's alright. Begin Game.
Firstly change the Medium Security prisoners Regime as follows:
00-06: Sleep; 07: Shower; 08: FreeTime; 09-10: Eat; 11-12: FreeTime; 13-16 Work; 17: Freetime; 18-19: Eat; 20-21: FreeTime; 22: Shower; 23: Sleep.
Next, build 10 more Serving Tables in both of the canteens and build 6 more Cookers in the Left side Kitchen. Hire 10 more Cooks in each Kitchen.
The above two instructions help fix some shortcomings of this map and reduce the likelihood of prisoners causing trouble or rioting too fast.
After that, clear away all the yards except the little one in the upper middle left of the left prison half (there are 6 yards in total in the beginning, 3 on each half; the little digit right above the yard room must be 1 after you clear the other yards).
To the left of the only Yard remaining, there is a cell block which can take 20 inmates. Go to Prison Running -> Security Sectors and make that cell block SuperMax.
Speed up the time to Fastest.
Schedule to Intake the maximum number of Medium and Maximum Security inmates available for the following days (you'll have to set this every in-game day).
New prisoners are brought in every day at 8:00. Every day for a few days, at this time or a few minutes after, go to Prison Running -> Prison Gangs and check the gang members entering your prison. Pick the gang that came in with the most members in the second day. Slow the time back to Normal. Change the Security for each member of that gang to SuperMax by selecting each member with
and going to Security, then adjusting it to SuperMax. Speed the time back up to Fastest.
Do the above two instructions every day until you gather 5 members of that one gang (for me it was the Reapers Gang; use Save and Continue Game right before 8:00 until you get more members of the same gang in that day's Intake, if the Intake contains over 20 inmates to save some time). Then go to Regime again and make one change to the SuperMax regime: Set Yard time from 11:00 to 17:00. Then, when that time hits, pay attention to your gang members in the SuperMax Cell Block and they should head to that small Yard right next to their Cell Block. Very shortly, the 'None' icon over there will change to the icon of that gang occupying that Yard.
Once that happens, press
on that icon, then press
to instruct your Guards to remove the gang from that area. Go to Emergencies -> Guard Response and spam
inside the Yard about 10 times to ensure enough Guards intervene in the gang removal. Since you start with a lot of Guards you will easily overwhelm the gang members and knock them unconscious. When all the gang members have been evicted, go to Regime -> SuperMax once again and turn all the Yard time into FreeTime. After some in-game hours pass, the Guards will take control of that Yard, the icon will change into the one of the Guards and the achievement will unlock.