There are several ways to make a wine bottle stopper. This is an example using a Pattern Bar (see pattern bar tutorial).

Wine Bottle Stopper Blank, Trough Antle Top(TMT) made by Aanraku Stained Glass (www.abasg.com)

The pattern bar was cut in half from corner to corner using a tile saw with a lapidary blade. This creates two bars, triangular in cross section.

Here are some sections cut from a different pattern bar. You need a section about 2 1/2" long.

The section was ground and polished on a lapidary wheel.

A wet belt sander would work also.

The bar has been glued to the stopper base with GE Silicone II Glue.