[XYZAidan] has a process that can recycle paper into 3D cardboard-like objects. You need a 3D printer, but it doesn’t actually print the paper. Instead, you use the printer to create a mold ...

Resin printers can create stamps too, just ensure a flexible material is used. What makes a good 3D-printed stamp? It should be easy to use, transfer an image cleanly, and retain ink reasonably well.