Step 2: The Shrink Process
Start by cutting off the bottom and inserting the wood plug.
I'm using a 2L milk bottle for a demo, so its way too big for the plug, but its just to show the procedure.
Next shrink the bottom of the bottle first to trap the plug inside. Then do the neck area, here I've cut off the threaded part to make the shrinking neater and easier.
One you're happy with the entire look its time to let it cool and the trim the waste so as to pop the mold off the plug.