Have a nice 9x12 folder that came sans viewing hood/back. But it did come with a pack film adapter. Any suggestions on how to make a ground glass back? What kind of glass? Or other material?
There's nice sellers on eBay who will make ground glass in any size. I was happy with glass I bought from photofinder on eBay, it's in my Pony Premo No. 4.
The trick will be mounting in you plate holder with the correct "register", so that the ground surface is the same distance in as the pack film would be.
As EASmithV has suggested, a sheet of ground glass in the film pack adapter is an easy solution. It is automatically set for the proper focal plane (same as the film pack would be) and the adapter fits the camera perfectly - no jury-rigging. The only drawback I have with the one I made is that the glass I used is somewhat heavier than standard and the back has no hood to darken the area around the image for work without a dark-cloth.
It's relatively easy to make a hood that'll fold into an old film pack (well at least the film packs I have). I've made replacement cloths for a few of my hoods and also a hood for a wodden quarter plate camera.
I have one or two spare 9x12 screens (Also 5x4 & 10x8) if anyone needs one (UK/EU).