You need sheets

It is not difficult to do this, since it is in every construction store. Its cost is not large, this is another plus of arched openings from Giparton. For the arch, you need sheets of material of different thicknesses. For the lower part, buy several sheets, the thickness of which is -9 mm, for the side parts, purchase a 12 millimeter drywall. You can also vary other options, it is already rely on your own imagination.