We first began, as always, using manipulatives. We have these wonderful one inch tiles that are perfect for creating arrays, but connecting cubes work as well. We discussed what the word "dimensions" mean when looking at the lengths of each side. We started by practicing arrays with smaller numbers and built our way up. Once I felt they understood, I put them in pairs and gave them each two numbers to find all the arrays for. An example of our work is shown below! (Please ignore the fact that the array she has showing shows 4x5 and is not an array for 18! She was actually building for their next number: 39)
If you have any suggestions for other awesome activities, or ways I can improve, please leave a comment below! Thank you!