If written English worked as written Spanish we would have a mark to differentiate between the “oo” in room and the “oo” in door. That would make life easier for many English students, no matter if they are native speakers or English as a second language learners.
Accent marks make reading in Spanish easier because they mark inflection points on the words. Even better, letters and letter combinations don’t change pronunciation in Spanish as much as in English: when you see an accent mark (or don’t see one at all) you just need to be careful about where the stressed syllable is. If there is an accent mark the answer is straightforward: where the accent mark is. When there is no accent mark, you have to know the rules to write it.
Rule one: When the stressed syllable is the last syllable of the word, and the word ends in a vowel or an n or an s, that word has an accent mark. For example: Canción (song), Nación (nation), Aquí (here), Allá (there), Inglés (English), Además (Also, furthermore).
Rule two: When the stressed syllable is the second from last syllable of the word and the word ends in a consonant other than s or n, then that word has an accent mark. For example: lápiz (pencil), árbol (tree), dólar (dollar), azúcar (sugar), cárcel (jail).
Rule three: Words with the stressed syllable on the third from last syllable always have an accent mark. For example: Química (Chemistry), Párrafo (Paragraph), Fórmula (Formula), Idéntico (Identical), éxito (Success).
There are other rules about special cases when the stressed syllable doesn’t comply with any of these three rules, but you can see those rules as exceptions almost always resolved with the addition of the accent mark. For our purposes, the exceptions are making our life even easier because they are telling us about the change on the pronunciation. For example words like tío (uncle), bíceps (biceps), dónde (where?).
Remember, we just need to follow the first statement: where you see the accent mark you need to put the stressed syllable there. With words with no accent marks, follow the rule backward to decide where the stressed syllable is.
For example, the word zanahoria (carrot). We don’t see an accent mark, so by definition, the stressed syllable is not the third from last (Neither is the fourth from last, those cases also can be considered exceptions and as exceptions, they will have an accent mark.) The word ends in a vowel and doesn’t have an accent mark, so the stressed syllable can’t be the last, -ria. Therefore, the stressed syllable is the second from last, ho, Za na /ho/ ria.
Let’s see two similar words, lápiz (pencil) and tapiz (tapestry or rug). Lápiz is straightforward: it has an accent mark, so you pronounce it /lá/ piz. But tapiz doesn’t have the accent mark. It ends with z. The first rule states that if the stressed syllable is the last one and the word ends in a vowel, n, or s, it has an accent mark. The second rule says if the stressed syllable is the second from last and the word ends in a consonant other than n or s, it has an accent mark. It ends in a consonant other than n or s and doesn’t have an accent mark in the second from last syllable. Therefore, the stressed syllable is the last one, ta /piz/, complying with the rule: it has no accent mark because the word doesn’t end in a vowel, n or s.
There are no shortcuts for this. You need to know the rules to use them. But if you master the rules, you will improve your pronunciation even with words you are reading for the first time.