It seems strange, but the slideshare instructions from Donna and the nearly same ones from Simon, have an error.
All of the MidSpiral objects need to be shifted 3.75 cm to the left. (Or at least the Mid spiral.)
All of the 3rd portion of the spiral, the InnerSpiral, and related objects, need to be shifted 1.875 cm to the left. (Or at least the inner spiral.)
So that the 3 turns of the spiral can be joined, without gaps
So the second and third center boxes are not "concentric".
(They did mention that the spiral had to be aligned.)

Donna:
https://www.slideshare.net/ambasadonna/constructing-an-ionic-volute

Simon:
https://www.slideshare.net/ozi/drawing-an-ionic-volute

Using Orient line-line, make copies checked, the moved MidSpiral objects were selected, the MidSpiral start and end used as Orient source line,
and the start and end of the OuterSpiral were used for the Orient target line, resulting in the InnerSpiral objects being created. (50% scale.)
The Groups, and Group names, used as the Orient source were duplicated in the Objects and Groups display, but can be renamed Inner...

- Brian