Full immersion English classes are when the teacher speaks only in English. The student learns English by speaking it, not memorizing and repeating grammar rules. Yes, grammar will be explained as needed, but it isn't the main focus. The main focus is speaking the language. This can be done by labeling items, repeating, & modeling how to say a word or phrase...which then leads to using sentences and having conversations.
Gestures (modeling actions) and drawing pictures can be helpful when explaining things. This can be used by both the teacher and the student to communicate. When I have a new student, I start off very animated, using many hand motions, and speak slowly and clearly. Once I judge the English level of the student, I can then adjust my actions and expression as needed. A more experienced English learner may not appreciate my slow speech and be ready for a more fluent conversation.
Another technique I use with new students, especially children, is I encourage them to bring items they like and enjoy to share in class. This can be a toy, drawing, book, photos...anything that the student likes. Then, I use that item to start our conversation, even if it is simply saying the name of the item, like "rabbit" or "book" while pointing to the object. I make sure to have many items on hand to use as examples.
We can build language like this:
Teacher: (while pointing to a book) "book" (prompt the student to repeat)
Teacher: "Great job!"
Teacher: (Gesture to the student to say) "I like this book"
Student: "I like this book"
Teacher: "Yes, very good!"
Through prompting, repeating, rewards and encouragement, full immersion classes can be fun and successful, even for new English learners.