The term tsuchioki (kanji: 土置き) means "putting dirt on" in English. It is written つちおき in hiragana. It's pronounced roughly like "tsoo-chee-oh-key".
Literally, laying down earth. 土, tsuchi, means earth or soil or dirt. Here it is referring to the clay (粘土, nendo, literally sticky earth) used during this important step in sword making.
The infinitive form of 置き is 置く, oku, “to lay down.” It can mean to physically lay something down, to leave aside, to fix (a target or a goal), or to employ someone, among many other meanings.