If you need really thin photographs on fibre base the easiest way is to make them on RC photographic paper and then do "emulsion stripping". RC paper can be split, starting at a corner or edge, and the picture can be peeled off. The "peel" is just the emulsion and a very thin layer of fibre base material.

I use this technique when mounting photographs on book pages which would otherwise become too thick and too stiff. Emulsion peeling needs some practice to do it consistently and it is much easier if you work with small photographs.