Learn Farsi: اکثر کارکنان امروز خسته هستند.

While aksar-e kârkonân is very common and completely correct, aksar can also function directly as a quantifier without the ezafe, similar to words like čand (some) or hič (no/none). Both forms mean exactly the same thing here.

How exactly is the word kârkonân built?

It is a compound noun made of kâr (work) plus kon, which is the present stem of kardan (to do). This forms kârkon (doer of work, employee). The suffix -ân is then added, which is the plural marker typically reserved for people.

This lesson focuses on nouns formed with a past stem plus -âr. Since kârkon uses a present stem, can we build an -âr noun from the same root verb?

Yes! The root verb here is kardan (to do). Its past stem is kard. Adding -âr gives us kerdâr (behavior or deeds), which is a manifestation noun. Notice how the present stem noun kârkon refers to the person doing the action, while the past stem noun kerdâr refers to the abstract manifestation of the action.

Could I use bištar-e instead of aksar in this sentence?

Absolutely. bištar-e kârkonân means exactly the same thing. aksar is an Arabic loanword, while is native Farsi, but they are fully interchangeable in this context.