The best way is to lead a whole pack into a taming pen. You tranq one and kill the other two, because one is on the ground the other two can die easy. You have time to kill them because you want to starve tame the allo.
Try to make them fall into a ravine. Flyers help with this tactic. Or better, look for some that spawned or fell into one. There’s a ravine on my SP game where there are around 11 allos that fell into it. After getting them into a ravine, kill off all but the one you’d like to tame. Proceed in taming as usual.
THE best way to tame anything is to use an argy cage, simply use like 5 dinosaur gateways made of stone and keep one gate door open before you find a dino to tame, once you do, lead it to the cage and then run out through one of the gaps between the gateway frames and obviously close the door and, tadaa, one stuck dino to tame
Make a taming pen with stone gateways, 2/4 on each side, 1 on the front side, and fill the back side with one doorframe with door and the rest walls. Place a large bear trap in the middle. Trap the allo in the pen in the bear trap so that you can safely close the front side gateway (the rest should be closed. If needed, kill the others. Make a foundation with a staircase on the backside. Now easily knock at tame the allo. This probably works for more dinos but only tried with allo.