Step 3: Wind the coil:
Cut a slot down one of the endcaps.
Leave 3" of wire hanging out of this slot and begin carefullly winding the coil. Winding this coil is probably the biggest pain in the ass of this project. I had many failures. There is a ton of information on the web about coil winding, but my best advice to you is go slow. The neater and tighter the wire is wrapped the more effective it will be.
When you get to the end of the coil tape your wire off and leave about 3" hanging off the end.