Learn Spanish (Spain): Son las once y todavía estás en la cama. - It is eleven o'clock and you are still in bed.

In Spanish, telling time is treated as a plural concept for any hour after one o'clock, because you are referring to the hours. Since eleven is more than one, you use the plural verb son (they are) and the plural feminine article las (matching the hidden word horas). You only use Es la for one o'clock, as in Es la una.

Why do we use estás instead of eres for "you are" here?

The verb estar is used to talk about physical location. Even though being in bed is a temporary state (which is another reason to use estar), the main rule here is that locations always take estar, never ser. So, because you are located en la cama, you must use estás.

Why is there a la in en la cama when the English translation is just "in bed"?

English often drops the word "the" when talking about routine places, like being "in bed", "at school", or "in hospital". Spanish does not drop the article in these situations. You must include the definite article and say en la cama, which literally means "in the bed".

Could I use aún instead of todavía in this sentence?

Yes! Both aún and todavía mean "still" in this context and are completely interchangeable. You will hear native speakers in Spain use both to mean that an action or situation is continuing.