I read about this technique here where it was used to look at stool samples on slides (fun!), but I mostly used it to look at color slides and other flat things. Below is a video of moving a slide photo of a building in front of the lens.
Step 1: Materials
- 3.0 mm ball lens
- double-sided foam tape (mine is removable)
- thin scrap pieces of plastic
- cheap retractable pen you don't mind breaking