There's a thick strip of adhesive along the antenna housing.

Insert a fifth opening pick in the top left corner of the rear cover between 8 mm and 10 mm (0.3–0.4 in) deep, or just over halfway between the tip of the pick and the iFixit logo.

If you can't insert the pick, start with the small gap near the camera bar from the previous pick.

Slide your pick halfway across the top edge to separate the antenna bracket adhesive. Stop at the halfway point along the top edge.