What is standard sample preparation protocol for super resolution microscopy?

Most are very similar. You can check the protocol we have used in follow publications:

Zhao, X., Garcia, J.Q., Royer, L.A., and Guo, S. (2022) Colocalization Analysis for Cryosectioned and Immunostained Tissue Samples with or without Label Retention Expansion Microscopy (LR-ExM) by JACoP. Bio-protocol 12(5): e4336. PMCID: PMC8918214.

Shi X, Li Q, Dai Z, Tran AA, Feng S, Ramirez AD, Lin Z, Wang X, Chow TT, Chen J, Kumar D, McColloch AR, Reiter JF, Huang EJ, Seiple IB, Huang B. Label-retention expansion microscopy. J Cell Biol. 2021 Sep 6;220(9):e202105067. doi: 10.1083/jcb.202105067. Epub 2021 Jul 6. PMID: 34228783; PMCID: PMC8266563.