Strongly recommend you cut mounts with a mount cutter - not scissors.
Again, if you are using black mounts on white paper, you will easily see the sides aren't parallel and it will stand out like a sore thumb.
Don't believe me? Go to eBay
and look at scanned pages of collections with mounts. Shouldn't take too much energy to find a page of scissor cut mounts. Makes me cringe every time as my OCD takes over.
I have two mount cutters - a large and a small. The large doesn't cut well under 30mm or so due to the clearance cut out for the blade.
You can try Hobby Lobby or Michael's as well in the scrap booking section. I have had terrible luck with rotary/slide cutters trying to cut mounts.
Suggest only getting a guillotine/swing arm style cutter. I have a larger (200 mm) and a small (100 mm) Lighthouse
I promise you will be glad you set aside the scissors!!!
Additionally, if you do use quadrille pages and scissors, the lines will show you your cuts are not square and you will see them every single time you look at those pages.
Good luck and show us a page!