Take a paper pattern modelled on the wrist of the patient.
After measuring, draw the shape on the software you like and design a solid form.
Print it flat, in PLA (for it's low glas temperature), and with solid infill (100% fill in Cura).
Dip the 3D-printed component in hot water, just under boiling temperature.
Take the piece out the water with tweezers (the print is still hot), shake it and wait a couple of seconds to drain all residuate of hot water and put directly on the wrist of the person to shape the part (you can also use a piece of fabric to protect the wrist from hot droplets).
Use your hand to form the support, and let it cool down to freeze the shape.
Repeat the procedure (dipping just the part to modify) until the form is correctly modelled.
