By forging only the folds the folded areas begin to curve. I'm only hammering the fold about 3/4 of an inch in from the fold. The untouched valleys will wrinkle, That's OK we have plans for that area. Work all five folds, anneal, repeat this three or more courses to get a nice curve to each fold. Note I rather like the hammer marks on the starfish I want the marks to be on both the right and left sides of each arm. I use a cross pein hammer for this. Anneal before going to the ball stake. The bowl is developed over a ball stake.