Lie supine on bench with head hanging off and knees and hips bent. Hold plate behind neck.
Flex waist to raise upper torso from bench. Keep low back on bench and raise torso up as high as possible. Return until back of shoulders contact padded incline board. Repeat.
Exercise can be performed without added weight until more resistance is needed. Certain individuals may need to keep their neck in neutral position with space between their chin and sternum. See Arm Position During Waist Exercises and Spot Reduction Myth.