Maybe the most simple way to explain sacred geometry in astrology is to show you what happens "picturewise" if you let two peoples charts overlay each other in a synastry chart.
For instance,if the resulting geometric picture of two peoples synastry-chart makes up a mandala,a geomatrix of pure equilibrium,it means the two people are to build perfected geometry together,it clearly means there is a great attraction between two people feeling being the perfect match to each other,may it be in a platonical relationship,or in a love-partnership.
Then,when discovering the compatibility of two people by drawing their together-geomatrix shown in the synastrychart,one can clearly see the complementing energies put together to create some kind of "greater harmony''.
This is why i always avoid to polarize in my astro-reports,instead i try to give geometric sollutions to difficult and tense aspects,be it a square or an erratic conjunction,one can always find a balancepoint that will enable the stargazer to create the needed setting in order to deal with tension most effortlessly.
I always found it hard in the past to listen to astrologers telling stories of doom and dark energies when it comes to saturn and pluto for example,yet,not one astrologer ever i found,to be willing to take a different look,a less polarized look,a more refined look,a deeper look that offers the best possible sollutions to tension and unease.
In my experience,me being a very librarian person,nothing is truely bad or very good in astrology,in my own view,it also always comes down to how we arrange energies by working with them in the best possible way.
These are examples of two different charts put together,forming sacred geometry
my geometry in astrology 2 is published here
https://www.academia.edu/49008361/Geometry_in_Astrology_2
Thank you Reiki Kiss !