I used books to hold my shelves in place while I put the screws in.
Below is the primed shoe bench looking up from the bottom!
Painting the primer took longer than I expected, and I had a disastrous time trying to clean up! I wish I'd thought to buy paint thinner before I had everything, including my hands, covered in oil-based primer... but from now on I'm armed with mineral spirits and latex gloves! I also learned that olive oil and salt will get the primer off your hands but not off your tools!
These supplies are actually clean in the picture above. I gave up when 99% of the paint was off!