You can develop color slide film as BW, but this need some additional steps for clear base.
1) bw developer
2) fix
3) c41 bleach
4) re-expose
5) redevelop

I found this procedure is unusable and processing expired Kodak E100D film as bw-slide. Its very easy and need less time:

1) 1st bw developer
2) dichromate bleach
3) clear bath
4) re-expose
5) redevelop

example of bw-slide from Kodak E100D as 200ASA