For "Do you like this fish sauce?" wouldn't "Placetisne hoc garum?" work better?
'Garum' is the subject here, so the verb needs to be in the third person. It doesn't work with 'placesne' or 'placetisne'.
'Is the fish sauce pleasing to you?'
Vobis is the dative (to you). This is also how the verb 'piacere' works in Italian.
Ok yeah that's my bad, I clicked the verb because when I originally saw it it didn't look right. And the top definition said I like, so I went with that and thought something went wrong with the question. Sorry