Both sides and on the bolt threads.
I prefer this sealant.
https://www.amazon.com/Permatex-80019-Aviation-Gasket-Sealant/dp/B000HBM3QQ/ref=asc_df_B000HBM3QQ/?tag=hyprod-20&linkCode=df0&hvadid=241895017383&hvpos=&hvnetw=g&hvrand=4607889600418835258&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9023812&hvtargid=pla-492732657309&psc=1