Step 1: Supplies & Getting Ready
A pair of Scissors and a knife
A roll of Tin Foil
a Marker (Washable, and very light color
Make your workspace clear and free of things such as lint or eraser bits. You will need some room. Set down a thing of newspapers so that you don't cut your surface or anything.
Don't cut yourself. Ever. EVAR! Simple enough. If you cut your finger off, it's your own fault.
Step 2: Casting the Top of the Hat
Note: Using tin foil and making a cast of a hat can save you the trouble of putting duct tape inside the hat to try to make a hat inside the hat. This works for any hat. It also doesn't make you look cheap by just duct taping the hat completly. That's called cheating.