Take the eyepiece out of the goggles and keep these plus the strap.
Paint the eyepieces (front and back) with the gold enamel paint. Mine needed a few coats.
Cut out the cardboard using the template here:
(you will need to size them for the goggles you end up using)
Cover the cardboard in leather, using as much as you need. I stuck it on with very strong glue.
Stick the eyepieces to the leather covered cardboard, find a way to attach the strap from the original welding goggles (I used two strips of leather) and enjoy!