Once stopped, the sequence matters. Turn the wheels away from traffic so the car cannot roll into the carriageway, get every passenger out through the doors on the barrier side, and stand behind the barrier, well behind the car, never between the car and oncoming traffic. Place your warning triangle far enough back that traffic sees it before it sees you, on a 120 km/h road that means much further than feels natural. At night, keep the hazards on and stay visible but off the tarmac. Stopping on the hard shoulder without a genuine emergency is itself a traffic offence in the UAE, so if police stop, explain the situation plainly.
Then decide honestly whether to change the wheel yourself. On a quiet street, changing a tyre is a fifteen-minute job. On the E311 shoulder with trucks passing an arm's length away, it is work for someone with a liveried vehicle, cones and practice, and a traffic-side rear puncture should almost never be a DIY job there. A callout to fit your spare typically runs AED 150-250, and many vendors can plug a simple tread puncture on the spot or bring a matching tyre for more. Modern cars with no spare at all, an increasing share of the market, take the decision out of your hands: you are booking a callout or a tow either way.