@Klei ah you are not ? Too bad

Cut the roll along its length . Open it and put foil on the inside surface ( this is for your popup flash reflection , lose the least light . If you don’t put foil , u might creat a snoot tube ^^) . Now the step b4 tape it back to its form.
fresnel lens , or magnifier lens was used to create the flash extender as u can see around the internet . If you can find a lens that could be fit inside the foil tube/roll , It will be great . If not , there is few options for you . 1 / Drop-in lens : in case that you found a rectangular lens , u can cut a hole on the tube anywhere you want . I prefer the further , the better . 2/ In the end lens : If it s way bigger than the tube ( I prefer the small one . We use the big one for a real flash extender).Just tape it on the side that you decide will be the end of the tube ( Cut the end like a flower then open up , put some glue/hot glue on , put the lens on )
Now u cantpe the roll back to its original form.
Ok, we need another tube for the rest .
We will put the foil onto it the same way we did above . but We need to cut it into some shapes before that . Cut along its length first . Shape 1 : we need to cut it in right-V shape , which create a 45* with the tube and bounce the flash 90* down to where we want. tape it on the end of your tube / lens . Another short tube for it to reach the ring .
Create the ring , another short tube( depends on your lens diameter) in the middle of the plate/bowl . Everything need to be cover with foil .
Sometimes, U just need some ideas and create your own style .