すみません、失敗してしまいました。これ、やり直せますか？ — Excuse me, I made a mistake. Can I restart this (or do it over)? (Traditional · Experience · Crafts, Formal — to staff, JLPT N4)

Gesture & etiquette

Point to the failed piece of pottery, look a bit apologetic.

Try to ask for help or clarification *before* making a major mistake if possible. Be aware that some specific stages of crafts might not allow complete restarts without extra cost or time.