Final answer:
To help Martin remember an idiom, the teacher should have him use it in context and apply mnemonic devices or imagery to make it memorable. Linking the idiom to a concept or story helps encode the material into memory more effectively, as does ensuring that Martin gets enough sleep for memory consolidation.
Step-by-step explanation:
The best strategy for helping Martin, a 5th grade ELL beginning reader, remember an idiom after it has been explained by the teacher is to have him use the idiom in context. By creating sentences or a story that includes the idiom or by associating it with a vivid image or concept, Martin can better encode the information in his memory. An example could be linking the idiom 'hit the hay', which means to go to bed, with an image of someone actually hitting a pile of hay before sleeping. This follows the concept that material is far better encoded when made meaningful, as demonstrated by the ease of recalling sentences when linked with prompts like 'bagpipe', 'ship christening', and 'parachutist'. Additionally, making use of mnemonic devices and getting enough sleep are essential strategies that aid memory retention and recall.