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.

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