Side plank:
Lie on your right side, legs extended and stacked from hip to feet. The elbow of your right arm is directly under your shoulder. Ensure your head is directly in line with your spine. Your left arm can be aligned along the left side of your body. Engage your abdominal muscles, drawing your navel toward your spine. Lift your hips and knees from the mat while exhaling. Your torso is straight in line with no sagging or bending. Hold the position for 15 seconds. It will be enough for a beginner.
Note that the elbow should be strictly under the shoulder joint, and the body should be tensioned as a string throughout the exercise. If you ruin the technique – stop the exercise immediately.

Side plank.