I would suggest looking at the first and second grade Singapore math textbooks for the strategies taught at those levels. In first grade, number bonds are used as a pictorial representation of what we call "fact families." The most important of these in first grade is number bonds which create 10. With my third grade class I dropped down to the unit at the end of 1B which teaches addition and subtraction facts within 100. Be sure to introduce the concepts with concrete materials, then go to the pictorial, then the abstract.
Singapore Math for Teachers by Teachers by SMARTTraining
