Yesterday’s oafishness had a predictable result: One of the panel pieces rode up ever so slightly in the rear, so I’ll need to plane that down a little more than desired. For the second drawer bottom, I came to my senses and did it this way:

This looks somewhat complicated, but it’s not. Instead of the twine that I was originally going to use, I used the ratcheting tie-down straps that I also use for securing lumber to my roof rack. The ratcheting mechanisms are underneath the bench, upside-down. It’s also a decent excuse for keeping weird little cut-offs around.
This method takes a little longer to set up, but is more effective, and is easier to manipulate.