This is quite a good video illustrating typical Corydoras spawning behaviours. In this excerpt, the female C. similis is searching for a suitable site to deposit the fertilized egg she is carrying in her pelvic fins. Near the end of the short video she selects the underside of a plant leaf, cleans it, then attaches the egg. The first part of the spawning process is not shown in this video, involving the laying and fertilizing of the egg in the "T" position, after which the female may carry from one to ten eggs to her chosen site. The males follow her as seen in this video.
We have had some threads about Corudoras spawning recently, so I hope this video will be of interest.