Build a 3x3 stone foundation on a raft, replace the foundation where you sit to control the raft with a stone hatchframe and hatch. Put stone walls 3x3 tall on the back of the raft, using 2 stone window frames and a stone doorframe/door on the bottom most lair. Put 2 stone fence foundations on each end of the walls, moving toward the front of the raft. Place a stone dino gateway and gate on each of those fence foundations. Place a wall 3 stone walls tall next to the dino gates, with stone window frames as the bottom layer. Place a wall 2 stone walls tall across the front of the raft. Place a row of 3 wooden ramps on the outside of the raft, starting at the top layer of walls on the front of the raft, down towards the water. Finally, place one layer of stone ceilings around the raft to the front, just before touching the ramps themselves. Now you can lure a Rex in there over the ramps, and escape on foot through the back door, or use a bird to lure it and land after it is caught.
If you use the bear trap strategy which is if you lead it into a Dino gateway that is shaped in a triangle and with a bear trap in the middle (Large Beartrap) and when it is stuck you must put a dinogate behind it to trap it and then knock out. (hope this helped and "If" I win could it be an Xbox voucher, thanks.)