Step 2: Break down your bike parts.
Lay your proto-belt out flat, then measure out the length you just calculated, starting at the valve stem. Mark and cut the tubing to that length. (Note: You're ignoring the 2-3" of tubing on the other side of the valve stem because that's going to be folded over later.)
From the tubing you have left-over, cut a 1"-wide section. This will be the...um...the little loop that you thread the tail of the belt through after it goes through the buckle. (Is there a word for that? If I poked the internet to dig up the proper word for that, would anyone know what I was talking about?)
For the sprocket, you may be able to find a lone sprocket wandering around, or you may have to detach it from a cassette and clean it up. You want one where the inner diameter is slightly smaller than the length of the valve stem.
For the bike chain bits, you can start with an old, worn, greasy chain and clean it up, or just buy a length of new chain -- less cleaning, more shiny! Since Fjord did all this work long before these pictures were taken, I don't have photos of the process. The idea is to take the chainbreaker tool, disassemble the chain, and separate out the flat top & bottom pieces of the chain. You'll then stitch the flat top & bottom pieces onto the belt with strips of rubber or elastic cord. Design your pattern first to figure out how many chain-bits you need; my belt has two rows with 22 chain-bits in each row, so 44 flat figure-8 chain-bits in total.