You have to know how to boneless 180 and boneless finger flip before you try this.
Do everything the same as a boneless 180. Then put your front foot on the ground grab and Indy. When you hop of you front foot do a regular boneless 180 but with your hand that's grabbing an Indy. Flip the board. This looks coolest when you spin the finger flip when you have already done a 90 in the air.