From the ESV Online Study Bible:
Mount Ebal is on the north side of Shechem (see 11:29 and note on 27:1–8). This ceremony occurs on the mountain of curse (see v. 13) to show that the law functions as a witness against Israel because of its inevitable sin.
wield no iron tool. Israel’s altars were to be of unhewn stone (Ex. 20:25).
Excavations at Mount Ebal have uncovered a worship site with a large altar (30 x 23 feet/9.1 x 7 m) constructed of unhewn stones, accessed by a gently sloping ramp. The pottery dates to the Israelite settlement (cf. Josh. 8:30–32). This perhaps is the altar that Joshua built or is built on top of Joshua’s altar.
And for another, “Shechem and mount ‘ebal in the bible: is this indeed Joshua’s altar?”
