Q1: Yes, based on its position, this could be interpreted as noun-adjective [freezer unwrapped]. However, in this context, an unwrapped steak makes sense and an unwrapped freezer does not.
Q2: Yes. "paper-towel lined" is a compound adjective.
Further comments:
The text "Put your freshly salted steak in the freezer ... " is correct and natural but awkward. Some editing improves the text.
First edit - Change the sequence [1 - put the stack on a rack; 2 - put the rack in the freezer.]
"Put your freshly salted steak unwrapped on a rack over a paper-towel lined baking sheet. Put everything in the freezer for 45 minutes, right before you intend to cook."
Second edit - Reword "paper-towel lined baking sheet"
"Put your freshly salted steak unwrapped on a rack over a baking sheet lined with a paper towel. Put everything in the freezer for 45 minutes, right before you intend to cook."