I just line the box with the trash bag ( like you would a trash can) and let the top of the bag hang over the top of the box. I then staple or tape the bag into place and trim off the excess where the box flaps attach. I salt my capes with mixing salt used for mixing with cattle grain. You can buy it at any farm supply store. I salt, hang for a day, then re-salt and hang again until almost stiff. Then I fold it and put it in the box and ship it.