Recently, we saw him teach a method for making large building blocks out of two milk cartons. I started saving milk cartons and other sturdy boxes to make my little ones a set of giant blocks as well.
First, I opened up one of the milk cartons and removed the plastic pour spout. Then I gently squeezed the top of the other one so I could easily stuff it into the first. I pushed it all the way down and used packing tape to secure the edges.