Cut meat into thin strips, about 1/8-inch-thick. Place strips in a shallow bowl. Combine salt, pepper, and garlic powder in a small bowl. Rub spice mixture into strips. Cover loosely with plastic wrap and marinate for 48 hours in the refrigerator.
Remove a rack from the oven. Preheat the oven to 115 degrees F. Remove the strips from the marinade and lay the strips directly on the oven rack. Place the rack in the oven, leaving it partially open to maintain a constant temperature of 110 to 115 degrees F. Leave in the oven until well dried, 10 to 12 hours.
NOTE: The USDA recommends cooking the beef jerky at 160 degrees F for the first 4 hours and then reducing the temperature to 130 degrees during the dehydrating process.
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