This is a case of 'things drawn that are impossible'. To get that shape you need at least two seams, or a bunch of darts, either way I can think of no method that will look exactly like that without some seams in there somewhere.
To make a paper pattern, start with a big sheet of paper long enough to wrap around your head. Tape it so it fits. Draw lines where the tail bits need to stop & start. For the top, I'd probably start with 8" of paper from the crown of your head to the top edge available to play with. fold in from various directions til you know how much excess you have, trim the extra off. Now you need to fold & crease till you get lines similar to the shape of the hat. draw on it plenty to mark fold spots, reference marks, etc. Once you've narrowed it down, you can unroll the paper, clean up the rough lines, and tranfer to a practice fabric to cut & sew.