If your cheese slices aren't large enough to make a satisfying taco shell, augment them with additional pieces laid so they touch. They are prettiest if folded so that the puffy top becomes the outside of the taco shell. The biggest trick is finding a material to which the cheese doesn't stick. However, greased waxed paper works. I've also had very good luck with the plastic wrap used to separate the cheese slices on every brand I've tried so far.
Some people use parchment paper or greased waxed paper.
Use paper plates covered with heavy-duty plastic wrap or parchmentm paper. Or use pyroceram. Be careful with any food that doesn't contain a lot of liquid. You can buy a year's supply of paper plates for the cost of just one Pyrex pie plate. Plus it makes cleanup so much easier.