how to teach "will" to pre-entry esol class
First of all, we need to know what you mean by 'pre-entry ESOL class'.
Secondly, we need to know what uses of 'will' you wish the learners to understand and use. You mention the future simple in your title. Are you aware that many grammarians today consider that English has no future tense? Teaching 'will' as the future simple can lead to problems for learners.