About an hour before you plan on eating, pull the deer steak from the fridge and let it rest on the counter until it comes up to room temperature.
Place a 10-inch cast-iron skillet in the oven and set the temperature to 450°.
Using a paper towel, blot any surface moisture and blood off steak. Rub both sides with canola or vegetable oil. Sprinkle heavily with salt and cracked pepper, pressing the seasonings into the meat with your hand.
When the oven comes up to temperature, carefully remove the hot pan to a stovetop burner set to medium-high.
Place the steak in the pan and sear one side quickly, no more than 30 seconds. Flip the steak and transfer the pan back into the oven. Cook about two minutes per side for medium rare, but no longer than 3 minutes per side.
Remove the pan from the oven and transfer the steak to a plate. Let the meat rest for about five minutes before slicing. Use this time to deglaze the pan with a little red wine or stock to make a quick, easy pan sauce.
Unwrap the steak and pat all surfaces dry with a paper towel. Place the steak on rack set inside a pan or on a small plate. You want the entire steak exposed to the air, plus the tray will catch any dripping blood or water. Set the tray in the refrigerator.
After 24 hours or so, check on the steak. It will probably be wet, so wipe it down with a paper towel. I also like to flip the piece of meat to ensure every bit is getting some air. Do this every day for however long you decide to age the steak. Five days is about the ideal target, although sometimes I will push it to seven. More than that and you're tempting fate with spoilage unless your aging conditions are exactly perfect. You'll also end up with an exterior that's too dry, meaning it will need to be trimmed before cooking. By keeping within the seven-day window, you shouldn't need to trim the surface at all. Just grill to medium-rare and enjoy.