The first three blocks glued by this method. Everything that follows depends on the success of this stage.
There are seven blocks, the leftmost I'm not putting an arch in due to its shape. That leaves six blocks with five arches.
I'll glue them in two sets of three to make them manageable and do four of the arches.
I've got a few ideas for putting them together. Either turning them over on the 12mm ply then sliding them off into position or leaving them upside down and using my supply of massive zip ties to brace them tightly to the ply and lower them into place.
Edit: I've been out to check, six do fit on that strip of ply and feels like they are within my lifting capacity so one helper should be enough. I flattened the tops of the first three before gluing and they fitted together much better than the next three, so obviously the filing first is useful.