Build a stone dino pen using fence foundations, door frames , dino gate. Then surround the outsides with stone pillars which you then use to place ceilings across the roof of the pen effectively beating the ravagers leap without the need to bola. Lure them in and lock the door behind them. Ive knocked out max level ravagers without issue using this method.
You don't need a large taming pen....
A 1x1 with door frames for walls. Put a ramp down on the side you will be running from. Seperate one and have it chase you. Stop at the top of the ramp. Jump down and though the opposite side door frame either at the last minute or just after it hits you. Knock it out (have 100 tran arrows just in case). Once it's out demolish the ramp, go inside and place wood spikes on four sides. Lie down inside and put in cook mutton and bio toxin/narcos. Once tamed, put on a saddle and jump out. Remove the wood spikes add a ramp and repeat.
I would recommend having a 2+ by 2+ with 3 door frames high and a small dino gate on one side. Remember the ramps. This will help make it a lot easier. If you build a wall around the pem then the animal should be safe.
Build a 4x4 pen 4 walls high (with doorways) build a ramp on one side and get a pack to agro on you. Have them chase you into the trap and run out the doorway. They take quite a bit of tranqs to knock out, but if you use cooked mutton they require no narcotics even for a 150.
A compound bow with tranq arrows can do wonders, but I'd still have a bola or two at the ready. I'd also have a dino, preferably a high damage raptor or scorpion for crowd control, just in case a pack shows up
Make a stone foundation and 4 doorways. Lure the ravager into the trap built from the foundation and three doorways and have a friend put in the final one. Now your ravager is stuck, easy to be ko'd and protected from threats. Bolas often dont work as the ravager can still attack and cant be bolad easily after escaping.