Best, as mentioned, to do the profile on a larger piece then trim to size...
If it is already a long narrow piece and it can't be done that way, I've attached to larger pieces with double sided tape. What you risk with that is breaking the piece while tryin to separate it again.
I have used the method of switching sides, if that seems safely possible... but if that doesn't seem possible or it can't be mounted to a larger piece, then I go back to making it on a larger piece and trim it to size (the safest method.)
"Don't worry, I saw this work in a cartoon once."
"Usually learning skills and tooling involves a progression of logical steps."