I know how ELISA can be used to detect particular antigens by using antibodies specific to the antigen.
How is it being used to detect SARS-CoV-2 specific antibodies?
I realise that one possible method could be using SARS-CoV-2 proteins and checking if any of the antibodies in the sample bind to it. Is this what is being done? If so, what methods are being used to mass produce needed antigens?
Finally, in the light of the above, why does the ELISA test for COVID have such high false positive rate?
[I will be grateful if the answer is a somewhat elaborate one, since this information doesn't seem to be easily available in the web or on YouTube: mostly the info is too simplistic, or rarely, it is too inaccessible.]