Flat Circle for the top:

Round 1 : Magic Loop and 11 DC in that loop  +Slip Stitch into the 3^rd chain
( Total 12 DC)

Round 2 :  Chain 3 + 1 DC in the same stitch + (2 DC) * around  + Slip Stitch into the 3^rd chain
( Total 24 DC )

Round 3 :  Chain 3 + 2 DC in the next stitch + (1 DC + 2 DC) * around + Slip Stitch into the 3^rd chain
( Total 36 DC )

Round 4 :  Chain 3 + 1 DC in the next stitch + 2 DC +
( 1 DC + 1DC + 2 DC)* around) + Slip Stitch into the 3^rd chain
( Total 48 DC )

Round 5 :  Chain 3 + 1 DC in the next stitch + 1 DC + 2 DC +
( 1 DC + 1DC + 1DC + 2 DC)* around + Slip Stitch into the 3^rd Chain.
( Total 60 DC)

Round 6 :  Chain 3 + 1 DC in the next stitch + 1 DC + 1 DC + 2 DC +
( 1 DC + 1DC + 1DC + 1 DC + 2 DC)* around + Slip Stitch into the 3^rd Chain.
(Total 72 DC)

Round 7 : Chain 3 + 1 DC in the next stitch + 1 DC + 1 DC + 1 DC +
2 DC +
(1 DC + 1DC + 1DC + 1 DC + 1DC + 2 DC)* around + Slip Stitch into the 3^rd Chain.
 (Total 84 stitches)

Hat Body

Round 1 :  Chain 3  +  Skip 2 Stitches  + ( 2 DC + CH 1 + 2 DC  – Shell) + (Skip 2 Stitches + 1 DC  + Skip 2 Stitches + Shell)* around  + Slip Stitch into the 3rd Chain.

Round 2 :  Ch 1 + Front Post Single Crochet ( FPST ) around the previous chain 3 + Ch 1 + Shell in the previous shell + (Front Post Double Crochet ( FPDT ) in the previous DC + Shell in the previous shell)* around  + Slip Stitch into the 3rd Chain.

Round 3 to Round 10 : Same as Round 2

Round 11 : To Flatten out
Ch 1 + Front Post Single Crochet ( FPST ) around the previous chain 3 + Ch 1 + [(1 HDC + 1 SC + SL ST + 1 SC + 1 HDC)  + FPDT in the previous DC]* around  + Slip Stitch into the 3rd Chain.