I did this trophy in the way RichSeventy4 described over on TA, and it's super simple.
Join a Friendy Free Roam lobby, this way other players can't kill you and aren't as likely to chase you.
Go to Blackwater and across of the train station you'll find a red brick building. Climb up both ladders to get to the rooftop. You'll see that it's a big rooftop with edges around. This provides enough cover for people to be unable to spot you from all sides.
For now, hop on one of the edges of the roof ( did it on the train station side) and shoot someone. Now the cops will be coming for you, though they'll come slowly. Keep killing until you reach your $1000 bounty and become a Public Enemy.
Now simple crouch and walk up to the middle of the rooftop area. Nobody is able to see you and for some reason nobody comes up the ladder either. So you'll lose your wanted level very fast and you'll be safe. Now you just have to afk for 10 minutes and pop goes the trophy!
You read that right, you don't have to be in Wanted for the 10 minutes!
Waiting 10 minutes and escaping the cops are two seperate things that the trophy wants. Thus even without using this method you should just try to escape ASAP once you become Public Enemy and then just hide until the 10 minutes are over.