Depending on the baby's age and development, their placement in the sling will look different.
Generally, we would recommend wearing your baby in a deep squat with knees above bottom, and with the baby's weight resting in the hammock of the sling.
Keep in mind that red lines on baby's legs don't always mean that baby is uncomfortable - they can be similar to the marks left on your ankles by your socks, or marks on your face left by a pillow.
That said, pay close attention to ensuring that baby has adequate circulation, an open airway, and is always visible and kissable.