Re: I'm an owner! 1975 Islander 22
Oh this new job is kicking my *** and my brain is fried.
Duct tape, PR. Cuz WD40 won't work for this one.
Pre-drill top of box, mount seat to swivel, slip bolts/washers - not screws, through swivel, tape bolts down unless you have really long, skinny fingers or small child to help, drop seat on box - make sure the bolts go in the holes, add nuts/washers, tighten everything (righty-tighty, lefty-loosey) down and give the seat a spin, whirl, whatever.
That's way more detail that you don't need PR, but your brain is fried. Trying to save your last brain cells for real important stuff, like battery placement.

Anyway, that's how I mounted seats and swivels on a box. HTH.