I did it for plastic bowl making in high school. Turned a concave bowl shape in a top section of wood. Drilled a lot of holes for the suction and built a sealed suction box around it with a port for a shop vac.
Hinged frame to clamp plastic plexiglass sheet which was heated up on a cookie tray in the oven
You can build a smaller version, but would need to carve out the design you want and modify as needed.
Trial and error to figure out heating time needed and proper temp to avoid major melting etc.
Waste of time for one knife, but if for a production series of knives. Could save on time
DON