Ferrous gluconate is prescribed for anemia (ferrous sulfate is the most common in multivitamins). You could go to any number of stores close to you and find it in the supplements section.
https://pmc.ncbi.nlm.nih.gov/articles/PMC9818626/
And yeah, lye is used in many traditional food preservation and preparation techniques.
Chemistry aside, what I takeaway is that this is a wild process for a relatively tasteless product (compared to traditionally processed olives).
























I think you got your suffixes reversed there!
https://en.wikipedia.org/wiki/Ferrous