So, you're making paper banners, so to speak............
Very seldom do we cut a paper product on any of our machines, unless there is a backer, to prevent this problem you are describing. All paper banners, signs or whatever...... regardless of size or how many are cut by hand or some sorta paper cutter meant for this purpose. Your boss may have wanted to save money/time by using this method, but he didn't do his homework properly. Wanting to do something and only having partial information does not mean it's gonna work without a lotta time, headaches and lost money.
If you have a hundred or two of these and you don't have the proper equipment, you'll need to get a cutter of whatever size required and start cutting. A hundred or two, shouldn't take more than maybe 2 or 3 hours. How many hours have you wasted trying to figure out something which is not meant to be done, already ?? It looks like you have over 24 hours in it already and you're not any further, than yesterday morning. Just start printing and get somebody cutting. Besides, it'll build muscles, so you're doing two things at once. Making money while exercising.