Bottom-up processing is not thought to be a very efficient way to approach a text initially, and is often contrasted with top-down processing, which is thought to be more efficient.
Example
Asking learners to read aloud may encourage bottom-up processing because they focus on word forms, not meaning.
In the classroom
Learners can be encouraged to use both bottom-up and top-down strategies to help them understand a text. For example in a reading comprehension learners use their knowledge of the genre to predict what will be in the text (top-down), and their understanding of affixation to guess meaning (bottom-up).
See also:
https://www.teachingenglish.org.uk/article/top-down
Further links:
https://www.teachingenglish.org.uk/article/teens-listening-skills