this is something I already found about a week ago, but couldn't manage to make anything out of it.
The spot is right before the slide into the village. You can walldash there again, and instead of entering the village, you are oob right next to the village (and are even able to enter the Roman Camp from there).
There is also a way to get to the village from there again (see second picture coming up in a sec).
In the entire time where you are oob Obelix will not teleport to you, he's stuck up the slide. Unfortunately he will teleport back to you once you are inside the official boundaries again.
The plan though is to talk to Fenr... Ferf... Frederik, let's call him that, and switch back to Obelix up the hill then.
But I just can't make it work. Please HELP ME! D:
The best I found yet is that Obelix also doesn't teleport to you when you hug the wall enough all the time, but Frederik is in the middle of the map...