Questions & Answers about Пирог был в духовке час.
Why isn't there a word for "for" before час?
In Russian, to state how long an action or state lasts (duration), we just put the time word in the Accusative case without any preposition. Because час is an inanimate masculine noun, its Accusative form looks exactly like the dictionary form (Nominative).
Could I use за час here instead?
No, because за + Accusative means "in an hour" (the time it takes to complete a result), which pairs with Perfective verbs. Here, "being in the oven" is an ongoing state, not a completed action, so we use the bare Accusative to mean "for an hour".
Why is it в духовке and not в духовку?
The pie is already sitting inside the oven, which is a static location. For locations (answering "where?"), we use в with the Prepositional case (в духовке). We would only use the Accusative (в духовку) if someone was actively putting the pie into the oven (destination).
Why does the sentence use был instead of было?
The past tense of быть (to be) has to match the gender of the subject. The subject here is пирог (pie), which ends in a consonant and is a masculine noun. Therefore, we use the masculine past tense form был.