Start with a simple gesture line for the pose
Block in the pelvis as a basic box or oval shape
Add two rounded forms for the glute masses
Place the buttocks under the lower back and above the thighs
Define the center crease lightly between the cheeks
Connect the outer curves into the hips and upper thighs
Keep the shapes symmetrical only when the pose is straight-on
Adjust the size and tilt to match the body angle
Add subtle shadows to separate the forms
Refine the contour lines and remove construction lines