The font used for the examples is my 'Bad Chess' font, with fallback to serif and then sans-serif fonts. The font is intended to demonstrate the use of the cmap table instead of the GSUB table to select glyphs from variation sequences.

The following three lines show, in order, three each of <U+2654 WHITE CHESS KING>, <U+2564, U+FE00 VARIATION SELECTOR-1> and <U+2564, U+FE01 VARIATION SELECTOR-2> along with a plain text comment. The default fallback for WHITE CHESS KING is ♔.

♔♔♔ - three chess kings. If from my font, they will be the same as the letter 'K'.

♔︀♔︀♔︀ - proposed variation sequence for white king on a 'white' square. The trio will be rendered the same as the letter 'W'.

♔︁♔︁♔︁ - proposed variation sequence for white king on a 'black' square. The trio will be rendered the same as the letter 'X'.

The font 'Bad Chess' is available for examination. It is a Microsoft-flavoured TrueType font - it has no GSUB, GPOS or GDEF table. Instead, a format 14 cmap subtable is used to provide direct mappings from and to their glyphs.

The font has no mappings for variation selectors on their own. Unfortunately, if the mapping for U+2564 is removed from the cmap table, then the mappings for <U+2564, U+FE00> and <U+2564, U+FE01> will be ignored.