Yes, many of us find it easier to break into multiple steps.  I believe that this is officially called the Laslo Technique

1. Tape off the deck, glue spacers together and clamp to deck.  DO NOT put glue between bottom spacer and deck.

2.  Once cured, remove specer assemby and clean up the edges with tools of your choice.

3. Now glue the lip to the spacer assembly and clamp back to deck.

4.  Once cured, remove the entire assembly and again clean up.  My favorite tool for smoothing the inside edge is the belt sander "professionally" taped to my tool box. 

5.  Remove the tape and glue assembly to the deck.

6.  Once cured, clean up the inside with tool of your choice.

7.  Cut strips of cloth on the 45 about 6" long and lay them around the lip and fold down onto the spacers.

I'm pretty sure I followed the "one-and-done" advice of the manual. I was careful to wipe epoxy drips away before they hardened and then I used a rasp to knock things into some sort of shape. Finally, I used a liberal application of "peanut butter epoxy" to fill in any gaps from uneven stacking. I used the vinyl glove alcohol rub to make the inside edge super smooth.   

Mark N provided a pretty comprehensive response here. That "Laslo" method is interesting, and if you have the time to stage things out it seems like that will surely produce high quality results.

FWIW I very recently completed this step on my own Shearwater Sport using the traditional method and did not find it to be unworkable. It was a bit cumbersome to move the glued (but still wet) assembly from a bench to its position on the deck as various parts did slip out of alignment. However, there was still plenty of time to finesse things back into position on-deck before clamping. Even some minor misalignment, such as spacers not being totally flush with each other around the inner rim, can be addressed during sanding.

As Birch2 mentioned, if you go the traditional route do be sure to diligently clean-up the squeezed epoxy on the outer surfaces with a gloved finger or something like that before the glue sets-up. You won't really be able to do this on the inner surfaces because the claps will be in the way, but you can still clean-up the outer edge reasonably well. I learned the hard way that any drips and blobs in this tight space are really challenging to deal with after everything cures.

You definitely don't need darts on the fiberglass cloth that goes over this coming. I had no trouble at all getting the glass to conform using strips about 6-12" in length cut on the bias. I put on 2 layers like this all the way around and it all went smoother than I expected.

As luck would have it, I did this today for my Wood Duckling, which is pretty similar to the Shearwater Sport, I think, aside from the fact that the manual doesn't recommend fiberglassing the coaming (as far as I can tell).

I clamped/glued the spacers first (in-place but on top of plastic, as discussed aboe).  I intended to glue the lip too but decided to break it into two steps since (1) my small batch of thickened epoxy was depleted and (2) the epoxy seemed to be hardening much faster than I expected in my 65-degree garage.

I left the spacers glued/clamped for 4 hours (with spring clamps as far as the eye could see).  I tried gluing the tiny vertical surfaces together at the front/back, but they didn't hold (which makes sense given the tiny surface area, now that I think about it).  I would recommend gluing only the horizontal surfaces of the spacers in step 1 and then gluing the tiny vertical surfaces (where the spacers meet in the front/back) only when you're ready to glue to lip to the top spacers (step 2).

I probably shouldn't be giving advice given that the jury is still out (whole assembly has been under clamps for about 4 hours).

I also fixed the hatch curvature today by putting some kerfs in it.  It felt like the most productive day in a while (I was really worried that the hatch fix might take ages).

   Thanks to all who offered advice.  I ended up doing kind of a hybrid of several of the suggestions.  I buttered up bottom surfaces on the four coaming spacers with thickened epoxy and set them on the boat.  Not having to fuss with the top ring made it pretty easy to get the four spacers in precise alignment.  They're all clamped up and setting now, for the past 3 hours or so.  I'll tidy up the edges tomorrow before I put the ring on.  So just one extra step.

Curious about Birch2's "vinyl glove alcohol rub" comment.  I'm using nitrile gloves.  Is the technique here to dip a finger in (denatured?) alcohol to smooth out the wet fillets?  I'd like to make a nice smooth fillet around the outside of the coaming underneath the lip.  I'm thinking a wood flour fillet would look better than a cell-o-fill, yes?

Also wondering about the cloth strip method for the coaming.  Not really sure what it means to "cut on the bias".  Can someone explaing?  Also, when using strips, don't you have issues with overlapping strips and frayed edges? 

Thanks again to all who took the time and trouble to reply.

Florida Jim,

Cutting fiberglass "on the bias" basically means cutting it at a 45-degree angle from a fiberglass cloth so the threads are at 45-degree angles relative to the ends/side.  The threads in the tape that ships with the kits are parallel/perpendicular to the ends/sides, but bias-cut fiberglass evidently conforms to curves much better.

https://www.clcboats.com/shoptips/epoxy_and_fiberglass/bias_weave_fiberglass.html

My Wood Duckling coaming done via "the Laszlo method" turned out well, by the way (pulled off the clamps today and set the coaming aside).

I had expected to put a single, huge fillet under the coaming, but it seems like it would be a big span to fill with a single (huge) fillet.  Might just add a lot of weight unnecessarily.  Given what I've seen in this thread and in the manual, it sounds like the preferred practice is to use two fillets - one on the top (under the lip) and one on the bottom (where the spacer meets the deck).  I have seen pictures of kayaks with cell-o-fill-thickened fillets on the coaming, and I think it looks pretty terrible (like a massive wad of glue, which is kinda what it is, I guess).  I plan to use wood flour to thicken for purely aesthetic reasons even though the (duckling) manual says to use cell-o-fill.  Then again, I certainly don't know what I'm doing here (this is my first kayak), so don't listen to me!

   Yes. You let the peanut butter epoxy get tacky. Then you dip your gloved fingers into denatured alcohol and rub the epoxy surface to get it smooth. If it gets too hard before you start, it won't work. And if you start too early, you might make a mess. But on tacky epoxy you can rub until the surface is glassy and smooth. Subsequent sanding is a breeze.