Actually, that's not true. Laminating the seat supports was actually the first step in constructing the bench. Because there are six supports (nine, actually: four under the seat, two lower supports, two test pieces, and a spare), and each one takes a day to clamp, cure, and glue. It made sense to begin with them.
Seat supports (with spares), glued up and ready to be trimmed and mortised.
The two side sections are glued up. I left the legs long so that I could trim them flush (and continue the sweep of the stretcher-curve) once everything was in place.
Once the tops of the legs are trimmed flush, I can mark the long stretchers with the approximate angle needed to bring them flush with the legs. I ended up ripping them as close as I could on the tablesaw, then planing them flush while everything was dry-clamped together.
Scribing the cut-line to fit the middle seat supports. I clamped the support to a "dummy" piece (the poplar right behind the stretcher), which was in turn clamped in between the two long stretchers.
Using a long piece of floating-tenon stock to mark out exactly where the tenon needs to go on the outside of the seat support.