Hello Greg! At the end of the Metru Toa Onewa instructions we can see on a preliminary (?) canister image and we can clearly see a giant robot’s head.
And on the front instruction page (which is the same with the canister one) we don’t see anything. Sure, it looks like the image was mirrored but wasn’t Metru Nui under Mata Nui? (In the Matoran Universe “brain”?)
In which case they were inside the giant robot, not outside.
Edited for Double Posting - Waj