One of the tricks I have come to rely on when making my own decals is to use a piece of foam board, like the type found in Michael’s Crafts or at WalMart in the office supplies aisles. This provides me with a nice flat surface to tape the printed decal paper on before overspraying with gloss clear coat.
I cut a 2’ x 3’ board into several different sized pieces- as when I print on the 8-1/2" x 11" decal paper, I then cut off the printed portion to preserve the remainder for re-use. Since most of my printing is done in portrait (vertical) format, my cut-offs tend to vary between 8-1/2" wide by 1"to 5" long. I let the printed (ink-jet) sheet air dry for 24 hrs, then cut off the unused portion and store it back in a plastic zip-lock type bag, away from light (either sunlight or artificial).
I then tape the printed piece of decal paper to the foam board with blue painter’s tape, and spray my gloss clear coat on- waiting another full 24 hrs to begin cutting and applying the decals on my project.
The foam board (in the cut down smaller pieces) provides a consistent flat surface for the clear-coated paper to rest on, which ensures an even thickness as the spray dries. Always set the sprayed paper-and-foam-board on a flat shelf, away from house traffic, so additional dust specks do not fall onto the drying surface. If you have a lot of carpeted rooms, make an effort to find a solid floored room space (hint- if teenagers are present, NOT the bathroom!) where less dust can be released from walking around.
One other idea- when I spray the clear coating, I usually do so in my large paint booth with the extraction fan running to remove the fumes from the spray. Do not let a fan (creating air movement) continue to play over the sprayed surface after you have completed spraying, as further air movement may (and it HAS happened