Step 2: Start head dome
Start by figuring out your head size. (side note: i cant give exact measurements for anything here, its completely up to your head size) then cut a rectangular piece of cardboard, the width of it should be long enough to go from the top of your head to the tip of your ear when curved, the length should be about an inch above your head size
Now draw a row of spikes on the cardboard, these should be an inch wide at the bottom and the tips should reach all the way to the top and be spaced an inch apart. Start the spikes an inch and a half from the bottom of the piece.
Now break the backing by running it down the edge of a table, see third photo. (credit for this technique goes to Seamster) you'll be using this technique for every piece
lay it out flat and cut the spikes out (as strait as possible) and then break the backing of all the spikes so they can curve inward.
(another side note) Don't worry too much about how the cardboard model looks because you'll be coating it in duct tape.