Took me about an hour, have added a few comments to the instructions. Phone seems to be working fine.

The metal fits under the black plastic near the screw shown to the left of the photo. When re-assembling, insert it back under here first, then lower the right-hand side back into place.

There is a clip near the top left screw - when you re-assemble, pop this back into place first.

Seemed to help to also pry the board up from the end by the screw hole near the antenna cables. Then it popped out.

With the phone laying flat on its back, insert the pick into the slot horizontally, then flip the pick upright, as per photo in step 4.

With the phone flat, screen up, insert the pick into the slot horizontally, then rotate the pick to the upright position, as shown in the photo in step 4.