The assumption that concrete was not available is probably correct but not certain. The Colosseum is largely concrete and the Pantheon (still) has the largest unreinforced concrete dome in the world. Wikipedia advises that concrete of some form was known in 6000 BC and that eg Bedouins used it to built underground cisterns in desert areas from around 700 BC. But, I could find no clear indication that it was used in India until relatively modern times.
The Taj Mahal was built over ~ 20 years from 1632 and Saint Paul's Cathedral in London was built a few decades later. Both are (as far as my non civil engineering eye and brain can tell - having looked at both) approximately equivalent accomplishments. I'd have expected something like cement would be a given in both cases. Maybe not.
A web search showed (as you also will have discovered) that there is a vast amount ABOUT the wells available but almost none of it deals with construction methods.
Better than most, but not really good enough, is Cyark's Rani ki Vav
An Ancient, Royal Stepwell which on that page gives an overview and on associated pages gives immense detail in cross section diagrams, photos, sketches and more.
3D interactive 'fly through' - impressive and fun - shows you WHAT was achieved but does not answer the 'how'.
All resources on one pahge, and you can subset them using the menu at top into 3D Point Clouds, Drawings, Panoramas, Perspectives, Photographs and Videos. Some of the detailed material requires an account but there is much there that is accessoible. Hopefully this approaches your "Stepwells 101" level.
What appears to be very close to what you want is described in a course outline, but without the detail in a school student's course outline. It's possible that the lecturer MAY make the course material avaialable. Course outline here - more questions than answers.
Form, Function, and Spirituality at Rani ki Vav
They say - After completing this lesson, the student will be able to:
describe well engineering and functionality with regard to several different
recall principles of weight bearing and the effect of water on various materials.
explain the history and construction of Rani ki Vav, the symbology of its iconography, and the source of its water.
relate the importance of water for survival to the prominent role water plays in religions across the globe.
compare the ceremonial aspects of carving across sites around the world, illustrating that the amount of effort placed into the creation of buildings may indicate something beyond its functionality.
reconstruct a scaled well or stepwell out of new material and engage the scientific method in testing its strengths and weaknesses.
Rani ki vav:
Archaeological survey of India
Minimal stepwell mention, but looks useful - Infinity Foundation sponsored new book project titled:
"Channeling Nature: Hydraulics, Traditional Knowledge Systems, And Water Resource Management in India – A Historical Perspective"
by Rima Hooja, PhD
Wikipedia - Stepwell
Your superb reference
Somewhat related only:
Cyark home page - just sit and watch