Maachalos Assuros 7:19

A butcher may not spread the fat from the flanks over the meat in order to make it more attractive. This is because the membrane over the fat is thin so it might break, causing the fat to seep out and into the meat. While it’s prohibited to do the things described in the past few halachos, the meat is not forbidden if they were done and the one who did them isn’t given stripes, though he is instructed not to do these things.

Maachalos Assuros 7:20

Meat may not be salted before the forbidden membranes and cords are removed; if meat was salted without removing them, they must be removed after salting. Even the sciatic nerve may be removed after salting and the meat then cooked.