Step 8: Punch A Hole Through The Gasket.
I recommend measuring before poking a hole to be as precise as possible. You can also remove the gaskets from both sides at the same time and lay them over each other and use the existing hole to mark where the new hole will go in the other with a ball point pen. Just make sure it's centered. It has some lines in it which can throw off visually where the center looks to be so measure your marking to make sure it's equidistant to both sides.
Placing the gasket over some cardboard can help ensure you don't stab yourself or scratch up the table you are working on.