This part is the BURN BOWL and serves two purposes. It initially is the internal primer area where alcohol burns to heat the alcohol to vaporization. It also serves as a heat sink, when heated by the jets, to keep the stove at at self-sustaining vaporization temperature.
1. Cut off the neck of one bottle. The cut should be at the tangent where the bottle neck just reaches full diameter.
2. Make a second cut at the top of the bottle opening as shown. This location is approximate. Start out with the cut a little long. it will be adjusted when fitting the burn bowl to the jet deck in step 8.