"It is on the bottom left."
In Japanese, diagonals are described as migi-ue, migi-shita, hidari-ue, and hidari-shita. Both Japanese and English have rules for which half to say first, to avoid mishearing or miscommunicating. It’s just that when the rule was made, English opted for vertical first, while Japanese decided on horizontal first.
This is a problem with having voices for "words" that really depend on what bigger thing they're part of. The parsing in these lessons isn't great, with words getting split nonsensically, so the readings are all messed up too. I know Japanese people don't always know how to parse their own language when teaching or transliterating it. Take the manga / anime series "Bokurano". the "no" in Bokurano is the particle の and is absolutely a separate word from 僕ら (we) even if it becomes a single word in English. They don't put spaces between words in written Japanese, and parsing is primarily done by Kanji, but linguistic analysis can tell you where the actual word borders are, and it's clear the (probably Japanese) person who made these lessons did not understand that, much like how a person who'd only known English would refer to other languages all having "prepositions" when they're only "prepositions" because they tend to come at the start of phrases in English. They're doing it from their perspective, not from a more objective linguistic one.
の is not "absolutely" a separate word; it is, like other Japanese particles, an enclitic, and "rests" on the word which it immediately follows (like the Saxon genitive "'s" in English or the Latin que "and").
I agree that splitting verb stems and conjugated suffixes isn't great, but in any case the grammatical situation can be quite a bit more complex than a preliminary analysis might seem to indicate, so I am hesitant to start assigning blame for decisions which have been made to try and adapt Duo's machinery to a language which works quite differently from the Spanish and English which Duo was first developed to teach.
I am confused by the choice of verb here - and the confusion is caused by another question in this lesson which asks us to translate "The chair is under that." In this question we appear to be talking about an agreed upon subject, "it". We have pointed at it, or asked about it already prior. And we are answering: "It is on the bottom left." Shouldn't this use です? The use of あります would imply to me that we are saying "There is a thing on the bottom left."
I had thought, perhaps, that "です" was simply not appropriate for specifying the place an object is in. But the "other question" I reference uses it in its answer. In that case, the "chair" is also understood to be an already introduced subject and です is used for indicating exactly where it can be found.
So - I suppose - this is a long way of asking why です is inappropriate as the verb in this answer.
I believe it would be "テーブルの上は左下に本があります"
My reason for thinking this is that you're talking about what's on the table (Since you said on the bottom left of the table) - you'd specify that first (テーブルの上は...), then the position (...左下...), then inform the listener that a book exists in said position (...に本があります).
Obviously since I'm still learning, if anyone knows better feel free to correct me! :P
I've been trying out Refold for a while, and its making me think differently about doulingo. Based on what I've heard people say during my active listening sessions, if a person was being asked where something was located...they would only say "左下" or "左下に." I feel like the latter should be an acceptable answer here, cause in speech it doesn't seem like "あります" is completely necessary.