My supplies. Just basic duct tape and a spare sketch pad I had lying around. Printer paper, notebook paper, etc works just as well, though.
Make and cut a strip that will be long enough to hold your nails in place.
Fold this strip horizontally into 1/3s. This doesn't have to be perfect by any means.
You should have something like this.
Then stick it to the paper and press it down to where it's pretty flat. You can see below, I made one for my cosplay's nails. (:
Make sure to separate them well enough that the polish won't stick together! (: best of luck! (: