As John recommends, gluing the irregular piece to a scrap that can be handled safely is probably the best method. I've made it a practice to use that method for anything irregular (shells, beads, etc.) that I want to use in either turning or other wood working/turning projects. Depending on the amount of holding power I need, I use anything from hot glue to CA. Haven't tried two sided tape yet but I ain't so sure I'd want to chance it.