Learn Hardcore Turkish: Teslimat bugün akşam saatlerinde yapılmalı.

-ler: plural marker
-i: 3rd-person singular possessive/definite marker
-nde: locative case (allomorph of -de)
So saat + ler + i + nde literally yields “in the hours.”

How is yapılmalı formed, and what nuance does it add?

yap (to do)
-ıl: passive voice suffix produces yapıl (to be done)
-malı: necessity suffix gives yapılmalı (must be done)
It expresses that the delivery must or should be carried out.

What is the difference between yapmalı and yapılmalı?

yapmalı: active necessity, meaning “someone must do it”
yapılmalı: passive necessity, focus shifts to the action itself (“it must be done”)

Why is there no explicit subject in this sentence?

In Turkish passive constructions with a necessity suffix, the agent is often irrelevant or unknown, so the subject (even a pronoun) is omitted.

Why does the verb appear at the end of the sentence?

Turkish follows a Subject-Object-Verb (SOV) order; even when subjects or objects are omitted, modifiers and phrases precede the verb, which stays clause-final.

How does akşam saatlerinde differ from bu akşam?

bu akşam refers to this evening, a specific point in time
akşam saatlerinde refers to the evening hours, an approximate range spanning several hours

Can the sentence be made more formal, and how?

Replace yapılmalı with yapılmalıdır by adding the formal suffix -dır.
Resulting sentence: Teslimat bugün akşam saatlerinde yapılmalıdır.
This version sounds more official or bureaucratic.

How else might you express the necessity using gerekmek?

Use a gerund plus gerekiyor:
Teslimat bugün akşam saatlerinde yapılması gerekiyor.
Here yapılması is the noun form of the verb, and gerekiyor means is needed.