To perform a Bent Knee Side Plank, start by lying on your side with your knees bent at a 90-degree angle and your feet stacked. Lift your hips off the ground, forming a straight line from your head to your knees, supporting your body weight on your forearm and the side of your bottom knee. Engage your core muscles to maintain stability and hold this position for a set duration, focusing on proper alignment and breathing throughout the exercise to effectively strengthen the obliques and stabilize the spine.