Measure your head. Divide the result by 3 and add a bit for seam allowance. This is the width of each hat section to cut.
Lay out your fabric pieces in a pile. The parts are symmetric so it doesn't matter which side of the fabric is up (and your fabric may not have a right & wrong side anyway).
Cut a pointy shape with divots, as pictured (it's not hard to understand, just hard to describe). You'll almost certainly make the hat too long, for some reason it's hard to underestimate the height of the crown. This is fine, we'll cut off any excess later.