The previous post may have been a bit opaque, here is a photo of the bench base right side up. The top is held in position by the posts and pads (on the bottom of the top, ugggh, see the last photo) rest on the flats (since the top is way non flat, I added pads and leveled them in relation to the top).
The are no fasteners attaching the top to the base, weight does that.
The posts seem pretty bomber as shown below (not real obvious but the base is leaning against the wall, where it has lived for the last couple of years provide habitat for dust bunnies and spiders):
And here is better view of the base/top connection (shown upside down):