Have a 3 micron thick plastic film that is 8mm by 8mm and I need to embed it into a standard micros

The film cannot wrinkle and a film area of 6mm by 6mm must be exposed to the air on the top and bottom.In other words I need to make a hole into a microscope slide and somehow embed a film, but have 6mm x 6mm exposed thus 2mm x 2mm of the film can be used for the embedding.

It does not have to be a microscope slide, but it can be any type of plastic or metal which can be molded or 3-D printed to embed the filter.