Dry-aged beef is exposed to air so dehydration can improve the beef’s flavor. Here’s one method suggested by Jennifer Armentrout at Fine Cooking:
Buy a prime boneless beef rib. Unwrap the beef, rinse it thoroughly, and use paper towels to pat it dry. Do not trim the fat off of the meat
Wrap the beef loosely in three layers of cheesecloth, and put it on a rack over a rimmed baking sheet. Next, place the beef in a refrigerator that is 40 degrees or cooler for three to seven days; the beef will become more flavorful as it ages longer.
After the first day of refrigeration, unwrap and then rewrap the beef with the same cheesecloth. This will ensure the cloth fibers do not stick to the meat.
When the aging process is complete, unwrap the cheesecloth from the beef and with a knife, shave off and discard the meat’s hard outer layer and its dried sections of fat. You have now dry-aged your beef.
Note that for safety reasons, you must cook or freeze the beef within seven days of beginning to dry-age the meat.