Summary

For these two, I took a pair of 3D modela, sliced them each into divisions equal to the material thickness, cut each slice, then reassembled the slices in order. By slicing to match the material thickness, it preserves the outlines, but not the full detail of the original models. Finer slices add more detail back, capturing more curves, while fewer slices causes the results to be more blocky.
Tricky parts:
Adding numbers to each slice so that each slice could be identified and put back in the proper order
Nesting as many cuts together as possible, so as to reduce wasted material.
Hollow models, like the hat, can make it difficult to reassemble due to the thin edges.