The British army issued foldable hexamine stove is a large version of the Esbit stove. It has a separate top plate that is designed to fit in a pattern 58 canteencup.
Since hexamine smells very badly and is considered toxic it would be better to use foldable stoves like this with alcohol. A hole of 69 mm in diameter will allow for inserting a Trangia B25 alcohol stove. This can be achieved with a 68 mm circle drill that is normally used for drilling holes for electrical sockets. A little widening of the hole with a hand file will make it fit for a Trangia burner.
More info:
www.youtube.com/Rifleman_Moore British Post WWII Folding Hexamine Cooker.
www.talesfromthesupplydepot.blog Folding Hexamine Cooker.
www.keymilitary.com Haute cuisine the British Army way.