Alright then.. OP...
I'll help you out since we both have base model 4Runners. Mine didn't come with a spoiler, either.
The spoiler mounts to the top of the hatch with 2 brackets. The brackets are screwed in to the hatch, not miraculously stuck on with tape. You must (as I did) drill the corresponding holes to mount the brackets. I did use double sided tape as a sort of gasket, however.
The spoiler then screws into the brackets. There are no specific giveaways or markings to show you where to drill, just line up where you can best eye it, mark, drill, and mount.
I did that with my base model and I guarantee that anyone could not tell the difference to that of a factory mounted spoiler.
Good luck.