I initially made this because I wanted to play around with the PVC I bought but it turned out pretty well so I decided to post it. Hence why I didn't document the earlier stages of the DIY. (:
You will need:
Transparent PVC, I got a 0.5mm table top protector
Studs with screws
On paper draw a rough trapezium around the glasses and mirror the shape for the closing flap.
Add the side flaps by drawing two more trapeziums, both with a downward slope.
Finally draw the bottom flap which should be about half the height of the main panel.
Cut out the template and make a mock case by folding the edges. Then trim any excess off if necessary. Tape the final template onto the PVC and then cut out.
Use the seam pickers or any thick needle and make a small hole where the black circles are.
Fold over the side flaps and screw the stud bases through the holes as pictured.
Screw the top studs onto the base.
Then fold the top flap over and use a hole punch to create a hole where the flap meets the stud.
A clear case for my clear sunnies!