Step 2: Make the pyramid
In this step I'm going to show you how I made the pyramid. First I cut out the four triangles. Because the box I was using for the base and top was rectangular I made a rectangular pyramid with two different sizes of triangle. Instead of just cutting triangles, I put two tags on each one, so that they would all interlock properly. Took a bit of head scratching but I got there in the end. For convenience I labelled the four sides N, S, E & W although I suppose ABCD or 1234 would have worked just as well.
For the base, I took one of the shallow boxes apart and cut the tags at an angle so they would fold in nicely. I also labelled them to match their triangles.
When this was done, I glued three of the four sides to make a big flat area, which was glued down and weighted with books. I glued it by interleaving the tags. You can see in photo 3 I also labelled the tags so I knew which tag went onto which side. You can see this shape in photo 2. When it was dry, I folded it up to make the final pyramid which was glued direct onto the base, again weighted with books. (My 2 year old was on hand to give advice)