Navasana or Boat is accomplished by coming to a straight seated position. Finding your sitz bones and bending you knees so your heals are just touching the mat. Krama.. 1. Sitting straight with your heart up extend your arms and tip back slightly engaging your core. 2. Raise your heals off the mat finding balance on your sitz bones. Do not lean back too far , you may over stress your low back 3. Extending your legs , maintaining that up lifting position breathing deeply and slowly. hold for 15 - 30 seconds, release and do it again.
Krama ( stages) are a very important factor in a safe Yoga practice. Know your body and it's limitations at that moment. Keep yourself safe at all times. If it hurts.... DON'T DO IT!!
Please add suggestions on the comments page. Om Shanti.. Tony