Learn Hardcore Chinese: fēngxiāng yǐqián xiě biāoqiān, yǐmiǎn ná cuò. - Write the labels before sealing the boxes so as to avoid taking the wrong one.

Breakdown of fēngxiāng yǐqián xiě biāoqiān, yǐmiǎn ná cuò.

Why is 以前 placed after 封箱?

In Chinese, 以前 often comes after a word or phrase to mean before that / before doing that.

So:

This is a very common pattern:

So here, 封箱以前写标签 means write the labels before sealing the box.

Is 封箱以前 a full clause, or just a time phrase?

It is functioning as a time phrase.

Together, 封箱以前 sets the time for the main action:

Chinese often uses this kind of phrase at the beginning of a sentence to give the time context first.

Why is there no subject like 你 or 我们?

Chinese very often omits the subject when it is obvious from context.

In a sentence like this, it sounds like an instruction, reminder, or procedure step, so the subject is understood:

English usually needs a subject, but Chinese often does not if the listener already knows who is supposed to do the action.

This makes the sentence sound natural and efficient.