‘ And Joshua made for himself flint knives, and circumcised the children of Israel at the hill of the foreskins.'
The action is depicted as Joshua's but he would no doubt be assisted by able and worthy men. The flint knives had to be fashioned and then all the uncircumcised males circumcised. During this period they would have been vulnerable (see Genesis 34:25). But YHWH had put such fear in the hearts of the Canaanites that they had nothing to fear.
“At the hill of the foreskins.” Literally ‘Gibeath-ha-araloth'. A name given to a hill where the practise was then carried out. It was possibly where the remnants were buried.