Learn French: Il est important que vous fassiez attention. - It is important that you pay attention.

The phrase Il est important que (It is important that) expresses a necessity or a subjective judgment. These types of impersonal expressions act as triggers that require the verb in the following clause to be in the subjunctive mood.

How is the subjunctive form fassiez constructed?

The verb faire (to do/make) is highly irregular in the subjunctive. Instead of taking its stem from the present tense ils form like most verbs, it uses the special irregular stem fass-. To this stem, we add the standard subjunctive ending for vous, which is -iez, giving us fassiez.

The English translation says "pay attention", but doesn't faire mean "to do" or "to make"?

That's right! In French, "to pay attention" or "to be careful" is expressed with the fixed phrase faire attention (literally "to make attention"). You cannot translate the English verb "pay" directly into French for this expression.

Could I say C'est important que... instead of Il est important que...?