I managed to get some foldscopes from a kickstarter box that made its way to Mexico. I gave one of them to my mother for her birthday. As they were part of a kit we didn’t have a preparation, but my family is familiar with microscopes. I prepared a very simple onion skin slide and my mother found a very old (5+ years) brine shrimp preparation in a glass slide. The results are good enough for a first try. We are already planning our first expedition!
Experience: Folding the foldoscope was a bit complicated, but the video solved all our doubts. It works very well with glass slides. Using a cellphone had some complications, mainly that the camera was not flat, but some tape solved that problem. I especially liked that it worked with a tablet so that my father, who has bad vision, could see our samples easily. Illumination is a concern, but one I am sure we will manage to solve.